Stand tall, keep your posture open and relaxed. No matter how terrified you feel, don't let it translate into defensive body language. Relax your face as well - a smile helps everyone feel at ease.
Scan the room, making regular eye contact with every pupil. Then, when you remove your gaze, the message is clear: "I'm waiting for you to pay attention". Perfect your deadly stare, so that a simple look tells an individual you are not impressed, without the rest of the class needing to know.
You can say a great deal with your hands: "five minutes left", "stop", "great stuff", "up you get". A quick tap on the desk of a recalcitrant pupil can indicate that you have spotted a problem.
Then there's the classic glance at the watch. Every pupil in every school across the land knows what that one means - "If you waste my time, I'll waste yours".
All that attention, without even opening your mouth.
Sue Cowley is an educational author, trainer and presenter. Her books include Guerilla Guide to Teaching (Continuum). For more information, visit www.suecowley.co.uk.