also, try browsing this forums and look for those threads that has alot of views on improving CTR tips. They've aided me in some of my placements.
You should first of all make sure you're making use of the AdSense channels. Don't just create 1 channel for all your ads but instead 1 for each ad. By this I mean that if you have a standard layout for all your pages of your site and for example have 3 ads, one below the header, one in the sidebar, and one in the footer, you should create 3 channels and name them appropriately (e.g. "header","sidebar" & "footer"). Once you've done that you can start playing around with placement and blending to achieve the best results. The best way to see which works best is to use A/B testing where you compare 2 variations at the same time. Always remember that ad optimization is an on going trial and error process. As trichnosis has already mentioned, section targeting would also be a good way to increase your CTR but ONLY if your ads are unrelated to your site content. Be careful when you implement section targeting though as incorrect use can make the relevancy of the ads worse. If any of the things I mentioned is still unclear to you, you could give my google adsense optimization page a read as it is a little more in depth there. Hope that helps Hodge