"The greatest teacher makes a few simple points. The powerful teacher leaves one or two fundamental truths. And the memorable teacher makes the point not by telling, but by helping their students discover on their own. Learning takes place through discovery, not when you're told something, but when you figure it out for yourself. All a really fine teacher does is to make suggestions, point out problems, above all, ask questions, and more questions and more questions...teaching encourages not only discovery but initiative."
From "Lend Me Your Ears" by William Safire