I have argued for quite some time that a good teacher is one that comes up with good questions, and a good question is one that is precise and fertile.
But, I always felt that this is only part of what makes a teacher good. I found the other part while reading Gessen's Perfect Rigor, where Sergei Rukshin reveals his secrets to success: listening.
Now, listening is an activity that requires patience, attentiveness, time, and honesty, and one should not confuse listening to hearing.
Note 1: I admit that the question posing as the title of this post is not a good one, precisely because of the adjective good.
Note 2: According to the book, Sergei Rukshin is the best mathematics coach in the world, having instructed students that went to win more than seventy medals in International Mathematical Olympiads.
