I make a little presentation on a topic, let's say nucleophilic substitution. I put notes on revision cards and then make a powerpoint, then I make my mum sit there while I tell her all about it. You've got to understand the topic yourself to be able to teach it, and even when I'm explaining it, the things I don't quite get fully end up clicking.
You remember:
20% of what you read
30% of what you hear
40% of what you see
50% of what you say
60% of what you do
and 90% of what you read, see, hear, say and do - pretty much teaching!