I recommend trying to solve problems. If you don't know how to solve a certain problem, join IRC, mailing list or some other math-related community. Look for humans rather than numbers. f(x)=y+5 are some dead characters that only make sense with some supplementary knowledge.

Books are good, but in the long run human communication is probably more important. You will eventually meet with a problem you can't solve or you might have questions or the answer might be unclear for some reason or another.