There are many sites claiming that they sell Adsense secrets. In my opinion, these secrets are plain common sense. Here's a few tips I picked up from some of these 'Adsense secret' sites.

1. Optimize your site (SEO) - Search engines such as Yahoo!, Google and MSN provide huge free traffic. Imagine listing your site in the top 10 search results, it would provide you tons of free traffic everyday. Higher traffic equals to higher clicks on your advertisements. You might wonder how to get listed in these search engines. Well I'm not the expert, so you might want to try on few other sites by searching Yahoo! or Google.

The easiest search engine to get listed in is MSN. Just go to the MSN website, and provide them with a link to your site. Submit your link here http://submitit.bcentral.com/msnsubmit.htm. They will probably list your site in their index within a week.

For Google, submit your link here http://www.google.com/addurl. Google is the second easiest search engine to be listed in and I noticed their bots or spiders keep coming to visit my site every other day. So it is a good sign as my site is being indexed into Google's directory.

For Yahoo! you can submit your link here http://search.yahoo.com/info/submit.html. Please log in your Yahoo! account in order to submit your link. For Yahoo! it might be a little tricky to get listed in their directory.

Also, search engines loves Meta tags. These tags are summary of your website and through these tags and the tag's description; it will help the search engine to locate your site. Don't forget H1, H2 and H3 tags are important too.

You can search for more info on other sites and combine all of these ideas and optimize your site.

2. Always place your Adsense advertisements in 'Strategic' locations. What I meant by strategic placement is don't place advertisements in hard to be seen areas. Usually place one advertisement at the right side and if possible make it nearer to the browser's scroll bar. That way, the user might accidentally click on those advertisements. Also try placing some advertisements in unexpected locations such as right in the middle of an article. So while the reader is reading your article, obviously he will notice the advertisement right away. Placing advertisements near any clicking areas also help. Try placing a Google Link ad near the 'Next' button or near any other link areas in your website. Making your Google advertisements less obvious by blending the colour of the text and link would also contribute more money into your Adsense. Finally, I've seen some slick people placing an advertisement right in front of a download link. Though the download link was big and 'white', the Google advertisement was right in front of it. I think it's not a violation, but heck, I was tricked into clicking it a few times - talk about effectiveness.
3. And finally, to get maximum profit from your Google clicks, keep track on the top paying keywords. I've seen some advertisements paying up to $60 per click. Most of these high paying advertisements are focused on insurance, loans, and legal advices.

Thus Adsense secrets are not a secret anymore - cause I've already told you about it in this article. So god speed and get more clicks on your site!