Much of your communication is done through body language. Be conscious before, during, and after your interview, to maintain strong body language that will help you make a positive, lasting impression on your interviewer.  Practice good posture by keeping your shoulders back, your back straight, and your chin up.  Don't keep anything in your lap like a briefcase or purse. Keep your hands and arms steady, and free of objects that you may subconsciously play with during your interview. First impressions go a long way, and one way to make a great one, is by greeting your interviewer with a handshake. This will show you are a confident, welcoming person. Practice your handshake with a friend to make sure it is not too soft, or aggressive. After your interview is over, follow up with your interviewer to show your appreciation, and once again, highlight why you are a strong candidate. You can send an email, or a card in the mail. However you chose to send it, be sure to do it within the next day.

Summary:
Display confident body language. Greet with a firm handshake. Send a thank you note.