When going on a interview it is important to remember that the non-verbal message can speak louder than the verbal messages you are sending. Keep in mind the following:

1. Have a firm handshake but not bone crushing
2. Stand and sit erect--a slouching posture makes you look tired and uninterested
3. Maintain good eye contact
4. It is natural to gesture or talk with your hands but avoid touching your face while talking as it will give the impression that you are trying to hide something.
5. Do not fidget

Practice before you go on the interview so these items become second nature.