adsense has not reached many even to the people who are with the computer science field and the concept not commendable yet with them.
If you can type it into the form, and Google doesn't spit it back out at you, you can use it (the only things you can't do that I'm aware of are setting colors to disguise text, ie white background and white URL or things like that)
Ad placement really depends on the type of site that you have. My bottom ads convert a lot better than my top ads because my readers actually read all the way to the bottom of the page.
You wanna increase your earnings? Stop tweaking your site to within an inch of its life and just work on getting more traffic. There. Just one step. Got it? Now stop wasting people's time with "tricks".
Haha yeah - the only thing I've done that actually, trackably increases my adsense revenue is increasing my traffic. If you just want to increase revenue, take those tips and put them in PDF... create a site and sell the PDF for $50.00 a download. Must work cause I keep seeing stuff like that EVERYWHERE.
Simple tips, i think they help, i once heard (well read!) of a guy who had text add very well blended in the site so people clicked on them without knowing it was an add... the result was that he got his account banned because he add continually more than one click from the same visitor. If is urban myth or not i dont know...either way i prefer to have my add "visible" well blended but not too much.
I usually use short article and using cloaked page (in other website) that redirect to that article. Very risky, but it work