Originally posted by kermi3
The best way to prove you know something and to be sure you'll remember is by teaching it.
It's also a very good test of knowledge, as other people have pointed out.

If you think you really understand something, very well, and your fairly confident about that subject. Try and explain it to somebody who doesn't know much about it, yet has half a brain. If you can get them to understand it fairly easily, then you not only understand that subject very well(since you can explain it 50 different ways), but you're also a good teacher, and smart in other areas. You're simply highly intelligent as you can relay information VIA articulate descriptions, pictures, going down the intelligence food chain and making it easy to understand for everyday joes, etc. etc.