Take control. You don't have to answer every question. Don't get steamrollered into saying things you're unsure of, but avoid saying 'no comment' - this will make you sound like a crook, even if the interview is about your promotion.
Less is more. Limit yourself to three key points, and make sure you get them across clearly. Cram too much in and you'll lose people's attention.
Stay professional. Be polite and amiable, but beware of treating your interviewer like a mate - you may drop your guard. Saying it off the record won't stop a sensational revelation appearing in print. If you don't want people to read about your boss' love of train-spotting, don't mention it.