Do your homework; be prepared...and amazing!
Residency programs schedule applicant interviews in different ways; some will contact you and others will expect you to contact them. When uncertain, it's appropriate to call and ask how the interviews are scheduled. The more places you interview, the better perspective you will gain of the program differences. While your GPA / rank, recommendation letters, clerkship knowledge, skills and performance played a major role in your securing the interview, how well you interview will more than likely determine whether or not you'll be ranked.
What to Wear to the Interview
For men, wear a nice-fitting suit (not a sports coat and khaki pants) in black, charcoal gray or navy blue (pinstripes are fine, too) with a white or pale blue collared shirt and a conservative tie. Hair should be short and it is preferred that you do not have a beard or goatee. For women, wear a figure-flattering suit in black, charcoal gray, navy blue or chocolate brown (skirt or pantsuit) with a simple collared blouse or shell in white or ivory. Shoes should be simple, low-heeled pumps. Jewelry should be conservative. Check out Men's Wearhouse and Ann Taylor for ideas and inspiration.
Travel to the Interview
Be creative and network with fellow students, classmates, alumni and anyone else you can find to assist with overnight housing. Plan to arrive in the city you're interviewing in a day ahead of time. Take an extra set of clothing with you on your trip. It may not be practical for you to purchase two of everything, but you should at least plan to pack an extra shirt and tie (or blouse) and socks (or nylons.)
Nature of the Interview
The interview process for residency programs is much like interviews for medical school. Typically, the department chairman or program director will greet applicants and provide a program overview. Then, some of the faculty members will be introduced. Residents usually take you on a tour of the facilities; this is the time to ask questions! No matter what they tell you, do not assume that the residents have no input in the selection process. Lunch and interviews usually follow. Be enthusiastic at all times and prepared to address any potential problems with your application. Be honest about the causes of any problems and be positive in your explanation. Your attitude will be remembered much longer than particular answers to questions. It's important to maintain contact with programs at which you do wish to train. It is also crucial to let them know that you are interested in them. The more interviewing you do, the better your perspective will be regarding what is available...and the more comfortable you will become with the process. You'll gain experience at less cost by interviewing at nearby programs early in the season.
Follow Up Correspondence
What happens between the interview and the match varies widely from specialty to specialty, and program to program. Some programs will send a form letter to everyone who was interviewed; some programs will make phone calls to the candidates they are interested in; some programs will do nothing at all. A thank you letter is always appropriate. If you are seriously interested in a particular program, say so in writing. However, most programs will say nothing about follow-up letters. Writing a "thank you" letter to your favorite programs is a common practice.
Websites to Check Out
AMA :: The Residency Interview...Making the Most of It
Careers in Medicine :: Resources for Interview Season
CiM Residency Interview Basics
Pinterest :: Women Preparing for Residency Interviews
What to Ask During Your Residency Interviews :: AAMC