The first thing to do right after the interview is to send a quick note thanking the interviewer for his or her time. This not only demonstrates your courtesy, but it also goes a long way toward making sure that the interviewer remembers you and keeps you in mind during the selection process. The note can be sent either via snail mail or email, whichever you feel is most appropriate. If the company seems very formal, then opt for a note on good paper, maybe handwritten or a hard copy letter. An email will usually suffice if the company is less formal.