Thank You Letter
Don't end the interview with just a handshake. Following up with a thank you letter is not only common courtesy but a true sign of closing the meeting professionally and courteously. A thank you letter should be a professional hand-written letter or email sent within 24 hours of the interview.
This is more important than you might think — when asked, most employers mention how much they like “thank you's" and how it helps them remember the candidate.