for me, a Chinese boy, how can i get high score in exam is the most significant. even i dont need understand what the teacher say in classroom, give me the books and lectures, i can learn them well. i know it's no good, but 4 most Chinese students, high sorce means everything, hope my suggestion can help u~

Attitude in teaching.  The teacher's dedication and commitment in teaching can be initially reflected by whether he is willing to spare a minute to leave a feedback on the classes taken and to respond to the stuents' simple message.  Otherwise, the students may feel they are just talking to a wall.  Of course, this is only a prerequisite.  There are still some other important criteria.

Hi Brenda Kletke

The most important quality in a teacher is the patience. He must to understand that if a guy want to learn an other language, he needs of time and training.

As far as I'm concerned, a good teacher must be enthusiastic; he/she shouln't seem like a traditional teacher. Secondly, he/she should provide proper feedback and adapt this to their students. Last but not least, have a good master of the language (native would be great or at least have very good experience).

I kind of agree with Carmen (I had my share of English teachers when I was a boy!). Simply telling me something and expecting me to be able to use it is naive. I had this when learning Romanian. I'd ask about a verb, and I'd receive a rapid-fire listing of all of the conjugations, which I had no chance of recalling, and the one I wanted to know was usually the first or second, so by the time the list was finished I still didn't know what to say.
I also had arguments with my wife (who is Romanian) because I would say something wrong and I knew immediately that it was wrong, but she would spit out the correct form at me before I could produce it myself. That's a good way to learn to continue to make mistakes.
I will never correct every single mistake on the spot. Parents don't do that with their children learning their native language, and people with whom you interact on the street in another country don't do that with foreigners. It's something completely foreign to any form of real conversation there is. I will happily tell students all of their mistakes after they finish speaking, but you know what happens? If someone says, "I tell my brother..." and later I draw their attention to it and manage to get the correct form, "I told my brother..." they say, "Well that's what I said."
But it's definitely true that the student correcting him/herself is more useful than me doing it, so I always ask what's wrong with the sentence, give a few seconds, and if I see that the information just isn't there, I provide it. When that happens, the best thing you can do as a student is to repeat the correct form a bunch of times, maybe even come up with a few more sentences using it in other ways. It will get easier and easier to remember each time.