I believe the first key is for one to actually like what they are doing. I have seen too many teachers in it for the wrong reasons, and that shows in the classroom, both with discipline and educational results.
As a teacher for 15 years, one thing I look for to determine my success as a teacher is how far the student has progressed. They might not always reached the predetermined benchmarks set forth by the Dept. of Ed., but if they have grown as a student (and as an individual) I feel they, and I, have succeeded.
Effective teaching engages all students regardless of their level. This not always possible, as some just fall behind, or don't bother, but I feel there is something that every student can excel at. I once had a student tell me that he started doing my work because I sent him on an errand to get my pocketbook. (I had left it in the classroom I was teaching in the pd. before.) He said that b/c I trusted him to do that, he felt safe trying to do the work even though he was terribly weak in all skills. I barely remember the incident, but this resulted in his working in my class and some of his others.
Students respond best when the environment is safe for them both physically and emotionally. Sometimes creating that environment takes time at the start of the new term, but it ultimately save a lot of time later on and thus creates an optimal learning environment that helps you accomplish more in the long run.
I could go on and on..... I hope this helps you.