AdSense

AdSense is an ad serving program run by Google. Website owners can enroll in this program to enable text, image and, more recently, video advertisements on their sites. These ads are administered by Google and generate revenue on either a per-click or per-thousand-impressions basis. Google is also currently beta-testing a cost-per-action based service.

Google utilizes its search technology to serve ads based on website content, the user's geographical location, and other factors. Those wanting to advertise with Google's targeted ad system may sign up through AdWords. AdSense has become a popular method of placing advertising on a website because the ads are less intrusive than most banners, and the content of the ads is often relevant to the website.

It currently uses JavaScript code to incorporate the advertisements into a participating site. If it is included on a site which has not yet been crawled by the Mediabot, it will temporarily display advertisements for charitable causes known as public service announcements (PSAs). (Note that the Mediabot is a separate crawler from the Googlebot that maintains Google's search index.)

Many sites use AdSense to monetize their content and some webmasters work hard to maximize their own AdSense income. They do this in three ways:

1. They use a wide range of traffic generating techniques including but not limited to online advertising.
2. They build valuable content on their sites; content which attracts AdSense ads and which pay out the most when they get clicked.
3. They use copy on their websites that encourage clicks on ads. Note that Google prohibits people from using phrases like "Click on my AdSense ads" to increase click rates. Phrases accepted are "Sponsored Links" and "Advertisements".

The source of all AdSense income is the AdWords program which in turn has a complex pricing model based on a Vickrey second price auction, in that it commands an advertiser to submit a sealed bid (not observable by competitors). Additionally, for any given click received, advertisers only pay one bid increment above the second-highest bid.

Contents [hide] 1 History 2 AdSense for feeds 3 AdSense for search 4 How AdSense works 5 Abuse 6 Criticism 7 See also 8 References 9 External links

[edit] History

The underlying technology behind AdSense was derived originally from WordNet and Simpli, a company started by the founder of Wordnet — George A. Miller — and a number of Professors and graduate students from Brown University, including James A. Anderson, Jeff Stibel and Steve Reiss. ^[1] A variation of this technology utilizing Wordnet was developed by Oingo, a small search engine company based in Santa Monica founded in 1998. ^[2] Oingo focused on semantic searches rather than brute force string searches. ^[3] Oingo changed its name to Applied Semantics, which was then bought by Google for an undisclosed amount in April 2003, to replace a similar system being developed in house. ^[4]

[edit] AdSense for feeds

In May 2005, Google unveiled AdSense for feeds, a version of AdSense that runs on RSS and Atom feeds that have more than 100 active subscribers. According to the Official Google Blog, "advertisers have their ads placed in the most appropriate feed articles; publishers are paid for their original content; readers see relevant advertising — and in the long run, more quality feeds to choose from".

AdSense for feeds works by inserting images into a feed. When the image is displayed by the reader/browser, Google writes the ad content into the image that it returns. The ad content is chosen based on the content of the feed surrounding the image. When the user clicks the image, he or she is redirected to the advertiser's site in the same way as regular AdSense ads.

[edit] AdSense for search

A companion to the regular AdSense program, AdSense for search lets website owners place Google search boxes on their pages. When a user searches the web or the site with the search box, Google shares any ad revenue it makes from those searches with the site owner. However, only if the ads on the page are clicked, the publisher is paid. Adsense does not pay publishers for mere searches.

[edit] How AdSense works

Each time a visitor visits a page with an AdSense tag, a piece of JavaScript writes an iframe tag, whose src attribute includes the URL of the page. Google's servers use a cache of the page for the URL or the keywords in the URL itself to determine a set of high-value keywords. (Some of the details are described in the AdSense patent.) If keywords have been cached already, ads are served for those keywords based on the AdWords bidding system.

[edit] Abuse

Some webmasters create sites tailored to lure searchers from Google and other engines onto their AdSense site to make money from clicks. These "zombie" sites often contain nothing but a large amount of interconnected, automated content (e.g.: A directory with content from the Open Directory Project, or scraper sites relying on RSS feeds for content). Possibly the most popular form of such "AdSense farms" are splogs ("spam blogs"), which are centered around known high-paying keywords. Also many sites use free content from other web sites, such as Wikipedia, to attract visitors. These and related approaches are considered to be search engine spam and can be reported to Google.

There have also been reports of Trojans engineered to produce fake Google ads that are formatted to look like legitimate ones. The Trojan Horse apparently downloads itself onto an unsuspecting computer through a web page and then replaces the original ads with its own set of malicious ads. ^[5]

[edit] Criticism

Due to concerns about click fraud, Google AdSense has been criticized by some SEO firms as a large source of what Google calls "invalid clicks" in which one company clicks on a rival's search engine ads to drive up its costs. ^[6] Some publishers have been blocked by Google, complaining that little justification or transparency was provided. ^[7]

To help prevent click fraud, publishers can choose from a number of click tracking programs. These programs will display detailed information about the visitors who click on the AdSense advertisements. Publishers can use that data to determine if they've been a victim of click fraud or not. There are a number of such commercial scripts available for purchase. An open source alternative is AdLogger.

Google has also come under fire for allowing advertisers to abuse trademarks. In 2004, Google started allowing advertisers to bid on any search terms, including the trademarks of their competitors. ^[8]

[edit] See also

• List of Google products
• AdSense for MediaWiki
• BidClix
• Kanoodle
• Yahoo! Search Marketing

AdWords

Video ads tips and tricks  Part 1 of 3

In July, Bismarck from the video ads team shared a few video ads best practices. Now he's back with a 3 part series full of new tips and tricks to help you make the most out of your video ad campaigns

An image is worth a thousand words. Now, how much is an image and a video worth? It’s been three months since we released video ads on the Google content network and we've seen a variety of interesting ads during that time – some that performed well and others that weren't quite ready for prime time. Over the next three weeks, we'll be sharing some of the key attributes of the ads that performed well. We'll start by sharing the tips below on creating rich and engaging video ads.

First, make sure that the opening image is engaging. Here are a few tips for the image:

• Memorable Image: Your opening image must capture the user's attention, and keep it.
   
• Vibrant Colors: The opening image has to entice users to hit play, so catch their eye with rich, sharp colors.
• Text: Although a stand-alone image can work as an opening image, we suggest that you include a few words to describe the product, service and/or company you are promoting.
• Call-to-Action: An opening image with a call-to-action is highly recommended. Informing the user that they can learn more by clicking play usually increases play rates.
• Multiple Sizes: In order to increase the number of placements where your ads can show, include an opening image in all of the following sizes 300x250, 250x250, 200x200 and 336x280. Please note that your image may be resized if it doesn't fit one of these sizes.

Second, you'll want to review these tips to ensure that the content of your video ad itself is as compelling as possible:
 

• Key Messages: Because users may not watch your entire video, make sure you deliver your key messages early in the video.
• Keep it Engaging: Video should be entertaining, informational, and relevant. Unlike TV advertising, you only have a captive audience if they choose to continue watching your ad. Whenever it appears on a site, your video ad will be your only communication with that site’s users, so it’s important to be clear about what your business offers. And remember, your audience won’t just respond to what you say, but how you say it.
• Short and Sweet: Although videos can be up to 2 minutes in length, we’ve found that users start dropping off significantly if ads are longer than 45 seconds.
• Make it Audible: Video ads allow you to use both sight and sound to communicate with your consumers – so make sure that the voices and/or soundtracks you use complement your overall message. If you are using a soundtrack, the music should not drown out any voices.
• Call-to-Action: Make sure you communicate to your users what you’d like for them to do – visit your store or site, call a phone number, complete a purchase – so they’ll have clear next-steps once the video’s completed.
   

  Video ads tips and tricks (part 2 of 3)

  Last week, we covered what it takes to develop a rich and engaging video ad. Now, in the second of three posts, Bismarck returns to talk about the types of metrics that can be tracked and optimized in order to maximize success.

  Since Google AdWords allows for real-time ad reporting and optimization, we want to make sure that you take advantage of the flexibility to improve your ads and media mix -- and get more out of your advertising campaigns.
  Here are several things that you may want to consider while managing your account:

  • Watch that play rate: If you find that your play rates start falling off, it probably means that the same users are seeing your opening image and don’t want to rewatch your video. If this is the case, try adding new video ads to your campaigns. If producing new video ads is not possible, then at least consider alternating between new opening images. You can also extend the reach of your campaign by either adding more sites with site targeting or new keywords that we can use to target your ads contextually.

  • Bid for Impressions: When you bid on a CPC (cost-per-click) basis, our technology tries to maximize the number of clickthroughs you’ll receive. If your ad fully conveys your message without requiring the user to click through to your site, this could lower your overall quality score and in turn signal our system to not serve your ad. With CPM (cost-per-thousand impressions) bidding, you assign a value to a user seeing your ad – our system then optimizes delivery in order to show the ad to more people. CPM bidding helps you maximize your exposure across sites in the Google content network.

  • Exclude irrelevant placements: By using negative keywords and the site exclusion tool you can block your ads from showing up alongside content that may not fit with your specific marketing objectives.

  • Focus on playback metrics: You probably want to increase the total amount of time that your audience spends engaging with your brand. By maximizing the duration and number of plays your video ads receive, you can achieve this goal. CTR (clickthrough rates) are important, but you shouldn’t weed out placements or sites based solely on an ad’s clickthrough rate.

• Video ads tips and tricks (part 3 of 3)

  Alas, our video ads series comes to a close today. In this final installment, Bismarck provides some quick tips to help you set up your video ad campaign.

  Running a successful video ad campaign isn’t just about creating engaging ads; your campaign settings are also crucial. Below are four tips to keep in mind when designing your campaign:

  • Geo-Targeting: When you set your language and location settings, focus your advertising to regions or areas where you conduct business.

  • Selecting Sites: If you’re using site targeting, use the site tool to select sites that are of interest to your audience. If there is a specific demographic that you’re trying to reach, use demographic site selection to find the right sites.

  • Selecting Keywords: If you’re running a keyword-targeted campaign, it is important that you have tightly formed AdGroups; make sure that all of the keywords in an AdGroup revolve around a specific theme or topic.

  • Bidding: Bid appropriately. Manage to cost-per-play goals: set the maximum you would like to pay per impression, but optimize to achieve target cost-per-play and audience reach goals.

Google AdWords provides one of the fastest mediums to getting an online marketing campaign up and running. Below are a few advanced tips that will help increase the effectiveness of a Google AdWords campaign.

 Dynamic Keyword insertion in Ad Copy

It is always beneficial when a searched keyword appears in the ad copy of a paid ad. Creatives in Google AdWords can be setup uniquely for every keyword, or a time saving strategy can be used to dynamically insert keywords into the text.

The syntax is: {keyword:Text to be displayed if the keyword searched is too long} {keyword} — displays the keyword or phrase in lower case {Keyword} — displays the first letter of the keyword or phrase in upper case {KeyWord} — displays the first letter of the keyword and the first letter of any other word in the phase in upper case {KEYWORD} — displays the entire keyword or phrase in upper case

Examples:

{KeyWord: Vacations} If the search term was "Trips" the ad would display: "Trips" If the search term was "Summer Vacations", the ad would display: "Summer Vacations" If the search term was "Where to find summer vacation deals", the ad would display: "Vacations" 

{Keyword:Vacations} If the search term was "Trips" the ad would display: "Trips" If the search term was "Summer Vacations", the ad would display: "Summer vacations" If the search term was "Where to find summer vacation deals", the ad would display: "Vacations"

Finding the "sweet spot" in Daily Budgets

If you are managing your Google AdWords campaigns to a daily budget, here is a tip to get more clicks for your money. Lower your maximum bid until you see your daily spend just barely reaches your daily budget. Do not focus on positions; focus on the value of traffic. It does not matter if you are position 2 or position 10 when it comes to the amount of visitors you can get for your budget.

Examples:

Max CPC is $1.00 and Daily Budget is $10.00 - This scenario produces 10 clicks by 10am and the account shuts off for the day.

 Max CPC is $0.10 and Daily Budget is $10.00 - Now the campaign had the ability to produce 100 clicks, but it turns out that only $5.00 is spent per day.

 Max CPC is $0.50 and Daily Budget is $10.00 - This turns out to be the sweet spot. Most days the campaign is on all day and reaches the maximum daily budget and receives 20 clicks.

As a bidding strategy, managing to daily budgets is not the optimal tactic, but it is a simple one that is easy to work with. Better tactics involve knowing the value of the clicks, conversions, and leads — maximizing ad spends while they are ROI positive.  

Lowering Contextual Bids

From the Campaign Management > Campaign Summary Tab, select "edit settings". If you are advertising in the "Content Network", select "Content Bids". Now you can go into each of your campaigns and set up maximum bids for the content network. These bids can be found in the ad group level. These bids can be significantly lower than the Search Network bids. There is a higher perceived value and more competition for the Search Network bids. 

Using the "if statement" when tracking the difference between search vs. contextual

To use this feature, you'll need to add an "if statement" to the URLs. For example, if your URL is www.domain.com, you can use the following parameter for your Destination URL: www.domain.com?type={ifsearch:GoogleAdWordsSearch}{ifcontent:GoogleAdWordsContent}.

This technique will allow for better tracking through the Web site's analytics tool. GoogleAdWordsSearch and GoogleAdWordsContent are variables that can be customized to the tracking requirements.

How to use Google AdWords

In an effort to find more customers for their business, many business owners start advertising campaigns in Internet.

SEO (search engine optimization) and SEM (search engine marketing) services are very hot and fashion and do a greate job for making themselves even more important for your business.

Many people spend a fortune to get huge traffic, huge number of visitors to their web sites but are doing a few sales only that even do not cover the PPC campaign expenses.

Here are a few tips and tricks that shall help you stay safe and profitable using Google’s AdWords and other similar programs.

1. As soon as create a new campaign in Google AdWords, edit the campaign settings and change the “Will run until” field to a reasonable date. Best, set it for one or two weeks maximum as at the beginning.

2. While in the “campaign settings” page - set your daily budget.

3. Set the target audience on the same page
» in the “Languages” list box, select the languages your customers might use and click “Save Changes”
» return to the same page again and set the locations, Countries and Territories where your ad shall be shown. Thus limit the people who click on your ad to those who might be interesting to buy your product or service.

4. Create different ad groups for the different products categories or services that you might advertise

5. In each ad group, set different keyword phrases to target one exact product or service. Do not advertise your web site itself. Advertise exact product or service and customize the landing link to point to its web page.

6. In each ad group, create different text ads advertising exactly one product or service. Create a descriptive text that illustrate what the customer will find when he/she visit the web page. Set a custom “Destination URL” that will bring the visitor to specific web page from your web site, reflecting exactly what the text ad advertise.

7. Check your Google AdWords (and other similar) advertisement campaigns on regular basis, once or several times per day. Make some fine settings, wait for some statistics, check the results and fine tune again.

To summarize:

Google say - create a web pages for the visitors, not for search engines!

No matter how many visitors you get. What really mater is how many of them will become customers and how many will just close the web page.

PPC, banners and other similar advertisement must say exactly what the visitor will find on your web site /better on the landing page/.

General or Niche Adwords Pages

You can build your website around general topics or niche ones. Generally speaking niche websites work better with adsense.

First off the ad targeting is much better. Secondly as you have a narrow focus your writing naturally becomes more expert in nature. Hopefully this makes you more authority in your field.

If this is your first try at building an adsense website, make it about something you enjoy. It will make the process much easier and less painful to accomplish. You should however make sure that your topic has enough of an ad inventory and the payout is at a level you are comfortable with. You may love medieval folk dancing, but the pool of advertisers for that subject is very small (in fact it’s currently zero).

Once you’ve gotten the hang of how Adsense works on a website, you are going to want to dabble in some high paying keywords, you may even be tempted to buy a high paying keyword list. This does come with some dangers. First off the level of fraud is much higher on the big money terms. Secondly there is a distortion of the supply and demand relationship for these terms. Everyone wants ads on their website that make $35 or more a click, however the number of advertisers who are willing to pay that much is pretty limited. Additionally the competition for that traffic is going to be stiff. So, don’t try to run with the big dogs if you can’t keep up. If you have to ask if you’re a big dog, then chances are, you’re not. I have used a high dollar keywords report from cashkeywords.com and was pleased with my results (see cash keywords free offer recap).

New Sites, Files and Maintenance

When you’re building a new site don’t put adsense on it until it’s finished. In fact I’d go even farther and say don’t put adsense on it until you have built inbound links and started getting traffic. If you put up a website with “lorem ipsum” dummy or placeholder text, your adsense ads will almost certainly be off topic. This is often true for new files on existing websites, especially if the topic is new or different. It may take days or weeks for google’s media bot to come back to your page and get the ads properly targeted. TIP: If you start getting lots of traffic from a variety of IP’s you will speed this process up dramatically.

I like to build my sites using include files. I put the header, footer and navigation in common files. It makes it much easier to maintain and manage. I also like to put my adsense code in include files. If I want/need to change my adsense code, it’s only one file I have to work with. TIP: I also use programming to turn the adsense on or off. I can change one global variable to true or false and my adsense ads will appear or disappear.

Managing URL’s and channels

Adsense channels is one area where it’s really easy to go overboard with stats. You can set up URL channels to compare how one website is doing to another. You can also set up sub channels for each URL. If you wanted to you do something channels like this:

• domain1.com - 728 banner
• domain1.com - 336 block
• domain1.com - text link
• domain2.com - 728 banner
• domain2.com - image banner
• domain2.com - 336 block
• domain3.com - 300 block

While this is great for testing and knowing who clicks where and why, it makes your reporting a little wonky. Your total number will always be correct but when you look at your reports with a channel break down things will get displayed multiple times and not add up to correct total. Makes things pretty confusing, so decide if you really need/want that level of reporting detail. TIP: At the very least you want to know what URL is generating the income so be sure to enter distinct URL channels.

Site Design and Integration

Once you know you are going to put adsense on your website you’re going to have to consider where to put it. If this is new site it’s easier, if it’s an existing site it’s more difficult. While there are some people who will be able to do it, in most cases I’d say if you just slap the adsense code in, you’ll end up with a frankensite monster (props to Tedster of WMW for the buzzword). While every website is different, Google has published some heat maps showing the optimal locations. No surprise that the best spots are middle of the page and left hand side. Now I’ve done really well by placing it on the right, but you should know why you’re doing it that way before hand, and be prepared to change it if it doesn’t work out.

Google has also has published a list of the highest performing ad sizes:

• 336×280 large rectangle
• 300×250 inline rectangle
• 160×600 wide skyscraper

From the sites that I run, I do really well with the 336 rectangle and 160 skyscraper. My next best performing ad size is the 728 leaderboard, I don’t really use the 300 inline rectangle too often. So really it depends on how well you integrate these into your site. Placement can have a dramatic effect on performance. TIP: When working on a new site or new layout you may want to give each location it’s own channel for a little while until you understand the users behavior.

Another ‘trick’ that can increase your CTR is by blending your adsense into your body copy. For example if your body copy is black, remove the adsense border and make the title, text, and URL black.TIP: Try changing all of your page hyperlinks to a high contrast color (like dark red or a bold blue) then change the adsense title to the same color.

The one area where I’ve found blended ads don’t perform as well is forums, especially ones with a high volume of repeat members. Regular visitors develop banner blindness pretty quickly. One ‘trick’ to keep the ads from being ignored is to randomize the color and even the placement. As with any of the decisions about location, placement and color it’s a trade off. How much do you emphasize the ads without annoying your visitors. Remember it’s better to have a 1% CTR with 500 regular visitors as opposed to a 5% CTR with 50 visitors. TIP: For forums try placing the adsense ads directly above or below the the first forum thread.

Using Images

One of the latest ’secrets’ to make the rounds is using images placed directly above or below an adsense leaderboard. This has been used for a while but came out in a digital point forum thread where a member talked about quadrupling their CTR. Basically you set up the adsense code in a table with four images that line up directly with the ads. Whether or not this is deceptive is fuzzy and very subjective. Obviously four blinking arrows would be ‘enticing people to click’ and be against the adsense TOS. However placing pictures of 4 laptops over laptops ads isn’t, so use your best judgment here and look at it from the advertiser or Google’s perspective. If you have a question as to your implementation being ‘over the line’ write to adsense and ask them to take a look.

As far as using the images, I’ve done it and can tell you it definitely works. You get the best results when the images ‘complete the story the ads are telling’. For example if you have ads about apple pies, use pictures of freshly baked apple pies, instead of granny smith, Macintosh, pink lady, and braeburn apples. TIP: Don’t limit yourself to using images only on that size ad unit, it works just as well with the other sizes, like the 336 rectangle.

Added:
I got a little criticism for this and rightly so, as I wasn’t specific as I could have been. Do not use very identifiable brand name or products for your images. Use generic non-specific stock images whenever possible and appropriate.

Multiple Ad Units

Another way to increase ad revenue is to use multiple ad units. According to Google’s TOS you are allowed to post up to three ad units per page. Similar to standard search results the highest paying ad units will be served first and the lowest being served last. If there is enough of an ad inventory, place all three ad units. However you should pay attention to the payouts. Current assumption is you get 60% of the revenue (on a $0.05 click you get $0.03). So if a click from the third ad unit is only paying between 3 to 5 cents you may want to omit it from your page. This is one are where giving your ad units channels does have value. If one ad unit is getting a higher percentage of click throughs you’ll want to make sure the highest paying ads are being served there. TIP:Use CSS positioning to get your highest paying ads serving in the location with the highest CTR.
 

Adsense in RSS

With the growth of blogs and RSS feeds you’re starting to see adsense included in the feeds now. IMHO this doesn’t work, and here’s why:

• You only get to place one ad unit.
• You have no control over finding the ’sweet spot’ for the ad unit.
• The ads are usually poorly targeted (this is getting better).
• People develop ‘banner blindness’.

I know people like being able to read full postings in their feed reader, and there are at least a dozen other reasons for full posts from pleasing your users to mobile offline computing, all of which are completely valid. However if your website depends on generating adsense revenue to survive, then bring them to the site and show them the ads there.

Affiliate Sites

Placing Adsense on affiliate sites is tricky. Are you giving up a $10, $20, or $30 sale for a $1 click? This is something you have to test on your own to figure out. If you aren’t converting now it’s definitely worth a try. I like to use adsense on my article pages. For example let’s say you had an affiliate website where you sold shoes. You’re going to need some related articles to ‘flesh out’ the site. Things like ‘getting a shoe shine’ or ‘finding a shoe repair shop’ these are excellent spots for adsense. While you won’t get rich, they will usually provide a small steady income and cover things like hosting costs.TIP: If you find you have pages getting more than 50 clicks per month add more pages about this topic, and link the pages together. Mine you logs for the search terms used.

PPC Arbitrage

This is a dicey subject so I’m going to steer clear of precise examples. Basically you bid on low volume uber niche terms at a very low cost. You set up landing page that contains high payout ads for the related general topic. You are looking for terms with a large gap between the price you are bidding on adwords and the price you are getting on Adsense. If you pay $0.10 a click and get $1.00 a click you make $0.90 each click. To get your adsense ad approved you will need to ‘add some value’ along the way. You can make a killing or get taken to the cleaners with this one, so make sure you know what you are doing before you try it.

Added
728 leaderboard works very well if it is just above the end of the “above the fold” area on what would be considered your viewers average resolution/browser window size if there are few other enticing links above the fold. Makes for an interesting layout but if you’re building a site for AdSense it may be worth it. We consistently receive very
high CTRs from doing this.

Try to build sites that allow you to quickly try any and all of those locations outlined in the heatmap guide or at least allow you a wide degree of freedom to easily change ad/content locations.

Adsense Tips, Layout Optimization Tricks for Higher CTR

AdSense Optimization Tips (from google)

Google recently held a webinar for AdSense publishers. They gave out some adsense optimization tips that they have gathered over the past few years. The transcript is pretty lengthy, so here's the summary:

• Ad Location - "the middle, above the fold location perform best." Also "if you have an article page with a long body of text, the bottom of that article is actually pretty successful"
• Ad Formats - "the top three formats are the 336x280 that you see on the page; the 300x250 medium rectangle; and then the 160x600 wide skyscraper." Additionally "the wider ad formats are doing better than the other ones and the reason is that they actually take up fewer lines. And so with every additional line, you have a chance of losing that interested user."
• Ad Colors - Pick colors that blend well with the site. Matches the background color, and compliments the site. Make them feel like a part of the site. They give an example where a customer went from blended background to yellow, and clicks dropped 65%
• Ad Blindness - if the colors stick out too much, readers may immediatly identify them as ads and not even look at them. Also frequent readers may stop reading ads so you could alternate positioning and colors to get their attention. "The more you blend in with the site, the less chance that ad blindness will occur."
• Experiment - this was a big theme in the webinar echoed by all experts. Use channels to test different colors, positioning, and formats to find out what works best. They show that you can more than double your revenue just by finding the right color, position, format combo.
• Image Ads - If you want to maximize revenue they recommend turning them on. I personally disable them in my account, because I find them too distracting/annoying to the user. Yes you may increase your CPC, but you will probably decrease impressions over time.
• Link Units - Don't take up much space, and also "allows the user to refine what they're interested in. So if they may not be interested in specific ads on your page, they might be interested in a particular topic, and by clicking on a link unit and a link in the link unit, they'll be able to specify that they're interested in that specific topic and get a lot more options and variety on the ads that might appear." I also bet google remembers what they click on and then tries to generate better ads for the page... just my speculation.
• AdSense For Search - You can use this for your site search, and you get a percentage of ad clicks.
• Focus on Content - Duh!
• Don't click on your own ads - One of the callers asked the question "I was just noticing that someone asked about clicking on their own ads and it says you're not supposed to. And I don't remember reading that. And I occasionally do click on the ads... So is that detrimental in some way?" - I can't believe they said that to google. Google's response was: "Yes, that's sort of chief among the terms and conditions".
• Impression Counter - Google confirmed that Page Impressions are counted when a public service ad (or alternate ad url or color) is displayed.
• Your site is unique - all these things may not matter, the best location, format, and color is different for every site. So again, go experiment