AdSense Program Policy document addresses the kinds of things you shouldn’t pull in an attempt to encourage people to click on your ads. I know this is a little negative, but it’s important that you pay attention to these no-nos because ignoring them could have dire consequences.
You can’t point out ads. You can’t pay people to click your ads. You also can’t use any kind of misleading titling around the ads (for example, using a Favorite Sites title when the ads really are just advertisements), and you must be cautious about the graphics you include around ad blocks. If they’re at all misleading and appear to be associated with the ads, that’s more fodder for the banning machine.
In short, all you can really do to encourage ad unit clicks is to place the ads in the best possible locations. Make them appealing with the design tools that Google provides and then leave them alone. Much more than that and you run the risk of landing on Google’s black list.