A thank you letter should be mailed to all interviewers and
networking contacts within 48 hours after your meeting. This
can be a short handwritten note or a formal letter. Most
importantly, you want to thank the interviewer for his/her time,
highlight a point(s) raised or specific topic(s) covered within
your meeting and reiterate your interest in the position.
This will remind the interviewer who you are and demonstrate your
genuine interest in the company. Exercise care in writing
your follow-up letter, because this is your last opportunity to
showcase why you are the right one for the job.
For letter samples, please see a Career