I think the most important is to make the lesson interesting and be friendly to the students. I have a teacher who's really understanding and approachable, and our class loves him. As well as trying to make thing interesting for the class he gives great handouts and does little things for the class such as hole punching the handouts for us (most of us carry folders). When something is done right he always give praises and he encourages people to ask questions when they don't understand. When someone do ask a question he explains tirelessly until the person understands, even if it takes a long time.

He never puts a student down for a low mark, he tells them that he'll help them do better. But the thing is that actually put us (or me at least) under more pressure to do well because we don't want to disappoint him.

Sometimes when he lets us talk in class he joins in the conversation (and he's quite funny), and there's no I-am-older-and-I-have-more-power attitide. But the people in our class respect him more than any other meaner or stricter teacher in our school.