The most important point is which template you are using. The best way to learn how you get more click is try different position. Ä°f you still want to hear a plugin you can use might-adsense(i used it 3-4 years ago)
You may want to try quick adsense. It does almost everything you might be looking in any advertising plugin and the best part of it being that its extremely easy to use and configure. For some advanced usage you will find advertising manager to be a much better option.