There are a number of things you should do to make sure you are as prepared as possible.
Whether you are interviewing for a residency or for a job, preparation is key. You need to know about the hiring entity (residency program or hospital/clinic/company) and about yourself. The latter may seem obvious but, when you are nervous and confronted by an interviewer’s unexpected question, you may find yourself unable to think of a relevant situation or example from your past to relate. You may end up stammering and “ummming” at best or looking like a deer in the head lights at worse.
So, again, prepare.
Preparing for questions about yourself can help prevent or calm those jitters everyone suffers during an interview and permit you to appear poised and professional. Probably the most practical way to prepare for this aspect of your meeting is to stage mock interviews with fellow students or friends. This will point out possible weaknesses (Do you say “Like” or “You know” a lot?) and can simply make you feel more comfortable during the “real deal” since you’ve already gone through the experience. Ask for honest feedback. Don’t forget to ask them about things in addition to the content of your answer—speech patterns (Do you talk too quickly or quietly or use slang?), body language, etc. If possible, you may want to video or audio record the session so you can see and hear yourself as others do.
Learn what you can about their structure, program, clients, competitors, etc. During the interview you’ll then be able to talk with confidence about what makes them different/exciting to you, and you’ll be able to respond to interview questions with appropriate information and ask the interviewer suitable questions. You’ll also be better able to determine if the hiring entity and you are a good “fit.”
Here are some hints from Monster on how and what to research.
WikiHow also has some hints.
Your job references should be able to vouch for your skills, abilities and qualifications as they relate to the job you are applying for.