At the end of February I signed up for Google AdSense and added it to my site in the footer of all pages. What I didn’t want was to have this ad on mysite that was competing with the content, esp on my homepage.
Then one Sunday I decided to shake things up a bit. I removed the AdSense panel from the footer and moved it to the top of some templates (article & blog detail, links, etc), but left it in the footer of others (homepage). Those tiny changes have resulted in my clickthroughs bottoming out around at the previous max and maxing around 4-5 times more than the most I was getting previously! Just by moving the ad around! Yes, it’s helped my bottom line quite a bit too.