How should I study for these AP tests?

<p>As a junior I am taking AP United States History, AP English Language, AP Biology, and AP Art History (I want to get at least a 4 on each). How do you recommend I study for these test? are there any special books or online thing I can use. If you have taken one of these tests before please tell me how it was and what should I focus my majority of my time on. Have a Great Day!</p>