My adage has always been "if you can't teach it to someone with a minimal background, you don't really understand it." If I really need to study a topic, I prep

My adage has always been "if you can't teach it to someone with a minimal background, you don't really understand it." If I really need to study a topic, I prepare as if I was going to give a lecture on it. That usually makes it painfully obvious where the holes in what I know are.