AdSense Tip #1: Find your keywords
Before serving ads on a web page, check its keyword density. A free and advanced tool for finding the most prominent keywords in a page can be found here: SEO Density Analyzer.
AdSense Tip #2: Improve your keywords
Get keyword suggestions from Overture Search Inventory and from Google AdWords Sandbox. Get new keywords that can help you improve your ad relevance. Enter the keywords from [web page name]-adsense-keywords.txt and save the suggestions to [web page name]-adsense-suggestions.txt.
AdSense Tip #3: Keep your website focused on a theme
Use the keyword suggestions to enhance your web pages and to build theme-based content. And also try to get your keywords into the anchor text of your incoming links as much as possible. Don't forget that Google AdSense is keyword-targeted advertising: Google AdSense bases its advert topics on your websites content, this means that content-rich websites of a popular topic should attract a large amount of ads.