Here are the things which I use to keep my Adwords campaigns in line. They have worked well over the last year as I have increased my company's revenue ~10 fold and have been able to hold a consistent ROI over the course of that increase.

This page gives an in depth look at the various aspects of and current issues regarding Google and click fraud. Link: http://www.marketingpilgrim.com/index.php?tag=click-fraud