I hear some colleges offer tons of credit to their students, so much so that some students can come into college with Junior status. Other colleges can be stingy and will give you very little credit, if any. I heard MIT may give credit in some of its sciences but even a 5 on AP Calc BC will not garner you any credit (Hey, it's like THE best engineering school in the nation!)

So, check out your prospective colleges and look into their AP credit plans.

You can be exempt from taking lower level classes in a subject or you can be exempt from having to take any classes in a particular subject.

Top-tier schools will probably reward you less credit while lower-tier schools are always happy to give more credit. My friend, with great AP scores, was able to get 3rd year standing at a state school but was only able to get 1/2 a years of elective credit work rewarded via a top-level university.