Make your presence felt, unless you especially want to disappear. You'll probably have to stand at the front or sit on the front desk. Move around. Put your own energy and enthusiasm into the class while staying in touch with the students' reactions. Move away from students who are speaking, so they'll have to speak loudly enough that others will hear (esp. important in front). Keep your voice and face mobile.
Have students move around sometimes; think about bodies in classroom space; have them move foward; try different spatial arrangements, e.g., having everyone turn chairs to face center of room.
Pay attention to sound/noise issues. Shut the classroom doors. Check often that students across the room from speakers (including you) can hear.
Watch your own behavior carefully. Avoid anything that students could construe as harassment. Check the CSU policies on sexual harassment at www.colostate.edu/Orgs/FacultyCouncil/
Be careful not to teach to one side of the room (right if you're right-handed)-or to one gender.
Chat as students arrive. Move around a lot during group work and during in-class writing/quizzes.
Use the board, but do it quickly (abbreviations), so that your back isn't to the room too long; consider putting a short version of your agenda on the board (in small writing?) so that you don't have to stare at your notes to remind yourself; good warm-up is lists of stuff from class (themes, motifs, questions); let students use boards for group work; consider newsprint and markers/crayons for reporting.
Learn their names early on, and have them learn each other's; also have them link up with 2 others for phone checking on assignments.
Keep the classroom busy. It's a good idea to have at least one plan up your sleeve for variation if the pace flags. If you're giving a quiz, have students who finish look for something specific in the text (or a specific type of thing), and so on.
Expect things to take longer than you think they will, at least at first. But have an additional topic ready to go if you get ahead of yourself-perhaps, say, a pile of xeroxed poems or a couple of transparencies.
Think carefully how to handle questions about your authority; how to stop racist or otherwise offensive comments in class; explain assignments (Why do we have to . . .) and judgments (How do you know . . .).
Make sure the students know they need to bring their books. For this to work, they have to really need them. Use them in class.
Maybe give them a few Qs to think about for next day
Consider regular "debriefing" moments: did this work for you? What could we have done differently that would work better?
If they start packing before you're done, say something like "2 minutes please" or "we've still got 5 minutes, hang on" or make a joke.
If the class is really going badly, stop it; send them home or talk about why. If students are unprepared (all or a few), send them home. Pop quizzes can reward those who are prepared.
Think about having a mid-term course evaluation session; we could get trained in this by Bill Timpson.