This is the only way of communication that will lave a very positive effect on the selection committee and will leave an impression long enough to remember you on the rank submission day to rank you high enough to match. We are talking about the thank you cards that most AMGs and some IMGs send to keep their impression live in the memory of the staff they interviewed with. Typically medical students will send them first tie directly after the interview to the director and coordinator and everyone they interacted with during the interview including chiefs ad key staff then another time in February.  These letters should be as short as possible, not disturbing and good enough to keep a smile. The size should be small as in these THANK YOU CARDS, brief content and hand-written. This is a sample how it usually look like (it can be shorter, the better):

Dear Dr (Program director or coordinator, Chairman, Chief resident or other interviewers):

I would like to take this opportunity to thank you for inviting me to interview for .....residency.
I was very impressed with your program and thoroughly enjoyed my visit. I found the residents to be friendly and forthright in answering any and all of my questions.
The informal gathering afterward was an excellent way to obtain information in a more relaxed setting and learn about the nontechnical aspects of resident life in (the city).
I look forward to start my residency with lot of passion and expectations.

Sincerely,
Name
AAMC ID