I'm throwing my hat into the ring of what makes a good teacher (as told by fellow UHS grads here and here), and I'm going to take the analysis one step further. I'm going to tell you the way you can tell if a teacher is going to be good from day one.
What you want from a teacher in the first class is for him or her to apologize. You want your teacher to say, "I'm going to do some things in this class that may annoy you, offend you, and otherwise make you mad. I know because when I have taught this before, I have received feedback from some people telling me so. But this is the way that will help you learn the material the best (because of x, y, and z), so I'm going to stick with it."
My biology teacher this semester apologized for seemingly half of our first class for any times in the future when he may offend us. I was sort of weirded out. He turned out to be funny most of the time and downright hilarious the rest, despite the class's early meeting time. I suppose he felt obligated to apologize because he had offended students in the past, but I would much rather listen to an apology one day than an exhibit in self-censorship for a whole semester.
In this era of ratemyprofessor.com, it is easy for a teacher to take the easy route and acquiesce to every individual complaint, even if it means that the majority of the students will be less well off. It's not hard to play it safe.
So if a teacher apologizes the first day for why he's not going to play it safe, I would stick around. You might just learn something after all.