[mark_h]

I think this is also why "the best way to learn something is to have to teach it", or at least that's what I've found. When you start imagining what questions you might get asked, you begin uncovering all sorts of holes in your understanding, even if it's something you thought you understood but suddenly realise you couldn't explain.

[agumonkey]

Keen to 'you dont know something til you have to program it'

[robertskmiles]

Two halves of the same coin. Programming something is 'teaching' a computer to do it. Except a computer is in many ways the dumbest student possible; you have to spell everything out for it.

[lurker17]

In other ways it's also the smartest student possible: It never forgets or misunderstands what you tell it (unless you instruct it to forget something, or you don't say what you actually mean.)

[Natsu]

Taking something apart can also work for this. But it might require that you're the sort of person who is able to put it back together again afterwards.