For me, it depends on the subject. Because I'm weird.
For social studies related classes, usually just reviewing facts is enough to let me get good test/quiz scores.
For science classes, I review the topics that I had the most trouble with, because science comes naturally to me, so the rest is easy.
For math, since I struggle with that the most, I put the most study time into it. I take whatever topics from the class that confused me most, and just do random problems related to that topic. This actually helps a great deal.
