Trial and error for Google Adsense Optimization
There are numerous Google Adsense Optimization tips available online, most of them are generally applicable but if you want to fully optimized Google Adsense earnings, you need lots of trial and error for your website.
General optimization tips include blending your ads color with your website design, put in appropriate location, blend ads within contents, use of larger size ad units etc.
However note that the same rules might not apply for all the websites; it depends on your specific visitors behavior, which could be influenced by ages, ethnic, origins, as well as your website topic.
I once had 2 websites with same design and layout (including ads layout) but with different topic and very much different group of visitors. One of the website was doing well with the ads layout while the other performed poorly, and I had to fine tune it with different layout.
Also in general advice large rectangular ad units worked the best, but I have a particular website that have the highest CTR with a 125×125 button.
Also note that if your website has a high ratio of repeat visitors, it’s advisable to change your ad format (layout, color, background etc.) occasionally as your repeat visitors might be “ads-blind” after visiting your site for a while.
It’s essential to do some readings with Adsense optimization tips, but in the end it’s trial and error that’s going to determine the most optimized earnings for you. Good luck.