Following up. Following up after an interview is a great idea. It keeps you freshly in the mind of the interviewer, shows you are interested and indicates that you are proactive. One follow up is great. More is questionable to me, but might be OK to do others according to the industry. For example, in sales, tenacity can be of great value. But for most other positions, more than two is going to possibly draw the ire of the interviewer.