To be a good teacher you must have genuine concern for the welfare of your students. You also have to understand that teaching is more than just delivering endless rounds of lectures and giving the most punishing examinations to your students. What is more important is inspiring them to learn more and work hard to improve themselves.
One of my former professors told us that being a teacher is like being a doctor. But instead of curing illnesses, teachers cure ignorance. His words are like medicines that slowly kill the bacteria inside the diseased body.
The real achievement of a good teacher is seeing his or her students become good men and women and it can only be achieved by showing them how to become one. Of course, a good teacher works hard to improve his craft. It is often necessary to become an expert in the field where he teaches so as to earn the respect of his students and at the same time deliver the best lecture.