I believe that both making notes and making flashcards are suboptimal; the best (read: fastest) method I know is to read and understand what you want to learn, then close your eyes and recall everything in full detail (that is hard, and somewhat painful; you should try to remember something for at least few minutes before giving up). Re-read whatever you haven't remembered. Repeat until convergence.

In math, it helps to solve problems and find counterexamples to theorem conditions, because it leads to deeper understanding, which makes remembering significantly easier. Also try to make as much connections to already known facts and possible applications as possible: our memory is associative.