Be a hardass- be strict, but fair. Always hold your students accountable for what you cover in class. Always be prepared- know the text, material, and lesson plans for the whole year in advance, if possible. Your preparation -or lack of it- will show- Don't ever wing it.
If you are challenging, your students will respond, and you'll have a better time, too. Students and teachers EARN respect, they do NOT automatically deserve it.
Also, make sure the administration will back you up if there are any egregious school conduct violations, such as fighting, threats, etc. in the school, where you are present. If not, go find another job in another district, ASAP.
Also, don't let the principal ever see you in the office, unless it's to pick up your paycheck - or to pick up the state award for best teacher of the year. Principals and superintendents do not like dealing with teachers' problems at all (esp. classroom discipline), so, you are on your own, NO MATTER WHAT THEY TELL YOU. Don't dump discipline problems (and their perpetrators) on the front office- that's a good way to make enemies, really fast. Keep them in your classroom, and deal with them yourself. The office has enough to deal with already.
I would even be wary of older teachers' ideas and advice- keep your own counsel. Don't complain, always be pleasant, and remember, what works for other teachers (even what I'm telling you), might not work for you. Nonetheless, a good mentor and helpful relationships are beneficial.
Network like crazy, too; better jobs and opportunities usually come by word of mouth, despite the ads in the papers. Most education jobs are already a done deal by the time they hit the want ads. (Administrators, however, have to go through the motions of interviews, etc., in order to look fair.)
NEVER bring anything to school on you, nor say or write anything to ANYONE in the school, that could be misinterpreted. You are under a microscope at all times.
Back when I was teaching German, in my first year, a well-meaning relative in Germany sent me over a stack of youth magazines, (BRAVO, etc.) in a big envelope that I stuck in my briefcase, and brought to school, w/o looking at them first. (I thought I'd go over them in study hall, to see what aricles I could cut out and use in class.) Well, while I was helping out a student in class, some others saw the mags in my briecase and started looking at them. Lotsa nudie teen pics, it turned out (YIKES!!)--- teen mags had got a lot racier in Germany since I was a kid there...oy!
Reaction? let's just say... even in liberal MA., people are still pretty puritanical compared to Europe. I managed to salvage my rep as a good teacher and person, despite that incident, before it got too far, but I had to do some fast explaining to my dept. head.... yes, they shouldn't have got into my briefcase, but more importantly in today's political climate, I shouldn't have even brought them to school. (phew...)
Good luck- and be prepared!