Test, test, test

It turns out that the best way to prepare for a test is by doing practice tests.
At some level, I have known this subconsciously. Want to have a successful Math exam? Do practice questions until you're bored to death. Having a 5-chapter History exam tomorrow? Do practice questions until dawn.

I think this also applies to things in general: expertise comes from repeated doings. In other words, expertise comes from experience.