Well, there are so many adsense tips floating around. Still thought of compiling a list, from my own experience and from whatever I leaned from a lot of resources.
1. Adsense Heatmap
It may be told a number of times, but let me repeat - Adsense heatmap works!! I have increased CTR for a forum by almost 4 times by having ads just after the first post!
Here is the heatmap:
https://www.google.com/adsense/images/placement
and heatmap for forum:
http://www.google.com/images/adsense/en_us/support/forum_en.jpg
2. Use channels
Channels are great tools to track your performance. Use channels for each ad position and name them logically -"homepage-header-banner". Keep an eye on the performance over a period of time, say one week. Don't be afraid to experiment. Change the colors, blending, size and see which one perform best.
3. Section targeting
Are you not getting relevant ads on your site? Dont worry, you can use section targetting.
Keep your most important text inside section targeting tags:
Your text goes here.
For more info, please visit:
http://www.google.com/support/adsense/bin/answer.py?answer=23168
4. Less is More
Are you getting $0.03 clicks? Probably you are using too many ads on a single page. Even though google allow you to plance up to 3 ads on a page, better keep it to one or maximum two. That is the best way to make sure that your clicks get paid more. Make sure that the location where you get maximum clicks will be the first one to display ads. To make it clear, there should not be any ads above your best location, when you see the HTML source code.
5. Blend Your Ads
Blending the ads to your site converts the best. You may opt for the same background color as the site, same text color etc.
Another tip: Dark background colors and light fonts work best. For eg: Balck background and white text, for both your site content as well as ads. You may have a slightly different font color for ads(say yellow) to get noticed. It may not be easy on your visitors, but it converts well. if you are not expecting too many repeat visitors, this may be a good idea