You can find thousands of samples on the Internet. Just look for big websites (alexa x,xxx) and check how they're placing adsense. There are no magic formulas though, since each website looks different and has unique optimum placements. If you want to know for sure, the only way is to split test different placements and ad formats. Just change one thing at a time in your design and run A/B test on that. Setup two alternatives for this one thing you're changing, and see which one works best. Keep doing this for a while, and you can triple or quadruple your earnings, if you already got a decent stream of traffic!