A crucial part of teaching, of course, is what you say and how you say it.
In the rest of this article I would like to focus on two factors that contribute to what good teachers say and how they say it: experience[40] and good judgment.
It may seem surprising that one can speed the acquisition[41] of the former and that one can teach the latter, but I will make the argument below that one can do so and that doing so is useful to developing strong teaching in mathematics graduate students