After evaluating your interview and within 2 or 3 days of the interview it is a good idea to follow-up. Keep the lines of communication open between yourself and the employer. Below are some suggestions to consider when following up.
Send a follow-up "thank-you" letter to the employer. This shows interest and keeps your name fresh in their mind. Depending on the timeline for selection, you may want to do this by phone.
Refer to your post-interview evaluation notes to anticipate the employer's hesitations about you and attempt to overcome them in your follow-up.
The employer is looking for a person to match their requirements. If you were unable to expose some of your strengths that make that match, you can discuss them in your follow-up.
Mail your follow-up letter two days after the interview so that you are still on the employer's mind but do not appear too anxious.
You may want to call the employer 2-3 days after mailing your letter to inquire if they received it, when you could expect to hear from them, or if it would be possible to arrange a second meeting. Persistence may be necessary but do not appear to be pushy or impatient.