We had been using adsense for a long time, last year we were lucky to have made $1 to $2 a month.
However, we spent a lot fo time building up the site itself. Which promoted traffic and quality traffic at that.
The next thing we did was ad the adsense, we match the ads so that they are a part of the site, embed them into content an articles. Also keep them above the "fold" of the site.
I read a few adsense related books, and they all basically say the best thing to do is try all the different ad sizes, do not use images ( choose text ads only), and try them in all sorts of places on your site.
We are still redoing all our sites but the ones that we have completed have started to really bring in money.
It isnt $1000's a day but to me earning $20 to $30 a day is better than nothing! We have a website dealing in the greencard lottery that has an article section, we set this up according to the "experts" if you want to see it I can PM you, then you can see what I am talking about.
But all in all you just have to keep trying different things out to see whats going to work and what isnt.
Using Channels is a great way to track effectiveness of ads.
Good luck! But thats just my two cents
