You have one more opportunity to stand out in the interviewer's mind after your interview. Take a moment, a day or so later, to send a brief, professional thank you letter. ONLY 1 OUT OF 30 people interviewed send a thank you letter. If you are that 30th person you will be considered more favorably because of your courtesy and persistence. If the person was a friend or you know them on a personal level then a nice card is sufficient, but if they were unknown to you and part of a hiring team, the letter should be sincere but business like.