The only way I ever really understand a theorem is by blogging about it; this is what I did with the Polya Enumeration Theorem, for example, whose proof I hadn't followed very closely in my algebraic combinatorics class. They say the best way to learn something is to teach it, after all.
An interesting side effect is that usually while writing up the post I realize that the concept I'm trying to discuss relates to a lot of other things I'm interested in. Once I can place a theorem in a wide context like this it becomes much more meaningful.
