It is really important to send a thank you note after having your interview. Taking the time to do so shows you are genuinely interested in the position. Since most candidates interviewed will send a thank you note, if you don’t send one out, then you certainly won’t get the job.
According to a survey by online job-matching service, The Ladders, 75 percent of interviewers said that receiving a thank you letter from a candidate affects their decision-making process”
Source: http://www.businessnewsdaily.com/5578-sample-thank-you-letters.html#sthash.0dQGEPlF.dpuf
Use the thank you note as your opportunity to demonstrate why you are the best person for the job. Don’t make the letter too long but do send it within 24 hours of meeting the interviewer. To stand out among all the other thank you notes, use a nice note card and hand write it. Make sure you get the address information so the card gets to the interviewer(s) promptly. Make sure to pay attention to the tone of the interview. If the person was more serious than make sure your thank you note reflects the same tone. On the other hand, if they were more casual, then tone down your thank you note.
It is up for debate whether the note should be emailed or handwritten and mailed. This is up to you. The handwritten note can stand out in an employers’ mind. Try to use a reference that will stand out in the interviewers mind so she remembers your interview. Also, make sure to mention some of your strengths that will make you stand out above the rest.