Designing to maximize AdSense click-thru
If you're an AdSense advertiser, there's an eBook (PDF) that you should consider reading: Google AdSense Secrets or What Google Never Told You About Making Money with AdSense. I considered getting it a few months ago, but decided then not to spend the money. I did some reading online about how to boost my AdSense earnings, made some improvements, and saw some revenue increases.
Well, last month, I decided to fork over the cash and see what the book had to say (it has some nice guarantees if you'll follow the advice in it, so I felt safe). I already knew some of what the book teaches, and trying some of its advice reduced click-thru (so I switched those things back--not every "rule" applies equally on all websites, which, as the book teaches, is why you have to test your changes to find what works), but some of the changes I implemented based on the book's advice have have doubled the click-thru on some of my sites.
The book will definitely pay for itself. And it offers plenty more advice that I haven't gotten around to trying. Especially if you haven't put much thought into optimizing your AdSense ads, I highly recommend this eBook as an excellent compilation of lots of valuable AdSense knowledge. And even if you have, you'll probably find information to help you build your revenue even more.