For approximately 11 years I've been a public school teacher although now my time is limited to once a week on Saturdays where I work with terrific kids at a private prep school for elite NYC schools, a job I've held for 7 years. (Used to work summers and afternoons as well prior to becoming a full time attorney.)

I also worked 5 years in one of the best school districts in New York.  Prior to that I had been in a couple of other schools and to put it kindly, some of them were horribly run although there was one in a poor district that was run superbly because of the people in charge.  My general rule of education is this -- Schools are what they are for a reason.

From these wide experiences I grew from a novice teacher learning the ropes to someone who mastered the art of teaching and could be considered a master teacher by this point.  It doesn't happen overnight.  And from my observations and experience I have something to offer teachers to help them learn the craft.

1.  Treat kids the way you wanted to be treated as a kid - This is my guiding light.  Try to think back to when you were their age and ask yourself if you would want to be treated that way. 
2.  Care - It's that simple.  Kids know the people who care and the people that don't. They respect the former, they mock the latter.
3.  Be Yourself - Very often the bad administrators want you to be a clone of them.  The good administrators recognize that good teachers come in all varieties.  The clown needs to be a clown.  The disciplinarian needs to be a discipplanarian.
4.  Always Give Kids A Way Out -  Try to steer them in a different direction.  Encouragement works far more than punitive measures.  Phrase like "In the future" or "As a reminder for next time" or "That's okay so long as we learn from this" not only diffuse a potential current situation but decreases the odds of future problems.
5.  Do Not Take Anything Personally - If the kid insults you, don't take it personally. If a kid falls asleep in class, it may be because he was up all night and got not sleep not because your lesson sucks.  Separate the act from the person and your kids will learn to do the same.
6.  Know Which Battles to Pick - You have to know what you will insist upon and what you can let go.  Be smart, just because you see a minor infraction does not mean you have to acknowledge that you saw it.  You can play dumb.
7.  Be Honest - Kids are better judges of adults than adults are of adults. If you are a phony or liar, they will see through you.  Don't lie to them.  If it's something you don't want to answer, say you choose not to answer.  Also, it is okay to not know something.  If they ask you something and you don't know, don't fudge it.  Say you don't know.  Better yet, take it upon yourself to find out the answer and present it next time.
8.  Yelling Should Be Rare If At All - I have reached the point where I haven't yelled in years.  If they get loud, you get soft.  If you are admonishing them, do it in a quiet but stern voice.
9.  Be Prepared - You are teaching them to be prepared, they will follow you if you show them you come to class prepared.
10.  Don't Follow A Script - The biggest mistake in certain districts is that they want teachers to be robots who follow a manual.  Well what works in class A doesn't always work in class B.  Teachers should have a general idea of where they are going with a lesson but always willing to diverge if the topic or audience leads you in a different direction. 

11.  Yes You Can Smile + Laugh - I am not a believer in that crap of not smiling or laughing.  I'm joking with the kids on day one although my situation is different now in that I've had certain kids or siblings for multiple years.
12.  Solicit Input - Don't be afraid to ask other teachers for their opinions.  Moreover, don't be afraid to ask the kids for their opinion.  If they feel decisions come from them, the are more empowered.
13.  Keep Kids Interested + Involved - I have hundreds of little gimmicks I use to keep kids interested.  It could be a 10 second song, a quick dance, an impersonation, self deprecation, a game, etc...  If they are not interested, they are not learning.

There is so much more to add to this list.  Feel free to share your experiences.