Following an interview, promptly, which would be no later than within 2 business days, write the interviewer a letter expressing appreciation and thanks for the interview. The purpose of this letter is to:
•Show appreciation for the employer's interest in you.
•Reiterate your interest in the position and in the organization.
•Review or remind the employer about your qualifications for the position. If you thought of something you forgot to mention in the interview, mention it in your follow-up / thank-you letter.
•Demonstrate that you have good manners and know to write a thank-you letter.
•Follow up with any information the employer may have asked you to provide after the interview.
Here is a simple format
Thank you very much for the interview today. In reviewing the opportunity with [name of company], I am most eager to start. In closing, let me say that no matter how many people you interview, what their education or experience is, you won’t find anyone who wants to work for you more than I do.
Very truly yours,