Be in charge, but be calm and polite. Be courteous, repeat the question for the entire audience, admit when you don't know, ask the questioner to rephrase the question, direct the answer to the entire audience, and ask the questioner to talk to you after the session if the question turns into a bigger discussion. DO NOT give your audience an opportunity to interrupt, make up answers when you don't know, maintain eye contact with the questioner when you give your answer, and/or argue with a questioner.