I have read many forums and websites with tips for AdSense publishers and have never really undertake any of the suggestions they have given to increase clickthrough rate and therefore AdSense earnings. Well my brother did it to a couple of the sites, and I was shocked, clickthrough rate increased 3 fold and earnnigs are up 300% also. I am now kicking myself that I didnt follow these suggestions so much earlier. I can suggest following the guides and just trying them out and you will be so very pleasantly surprised, I was.