Make a good impression with your future employer, and send a thank you note after the job interview. Not only does it let them know that you're grateful for their time, but it shows that you're willing to make the extra effort and have good social skills.
Address your recipient formally (Mr. Anderson), and express your gratitude for their time. Specify your interest in the company and how you may relate or fit in. Remind them of high points in the interview, such as common interests. Wish them well in their search and express your interest in being a part of it.
Mail: As soon as possible (within a week is best).