OK i know everyone wants to increase their CTR everyone has tried blending placement etc... with either great success or very little.... one thing you cant forget is how does your site look??? I did and update of my site the look and feel of it, placement of ads, colors etc.. basically the same and my CTR has gone up 3% and this isn't jsut a few days i am consistently higher for past month now.... So if your site is basic... not much style and kind of blah do an update and give it a fresh look it could increase your CTR!!!
I find to have greater ctr with basic plain site without images and all. Really just content and ads even without header etc...