Shake hands firmly, but only if the interviewer makes the first gesture. Good posture and a smile help. Wait until a chair is offered before you sit down. Never smoke or chew gum during an interview. Look directly at the interviewer when speaking and keep your hands still.
Body language can say a lot.
Practice with a friend to see what your posture and movements are saying. Know the message your body language is giving the interviewer. Employers may ask about information on your application form or resume, but more important, they are interested in learning what is not on the application. Analyze your strengths and weaknesses, background, and personal aspirations and values. In other words, begin to formulate not only what you would like to do, but also what you feel you are best prepared to do.