At the risk of sounding trite....honestly, just be really confident in yourself. You've fought hard to get to this point. Go in there and be confident in yourself and your abilities. If you're plainly freaking out or looking really intimidated, and feeling that way, it will show and you'll be shaky on your answers. Don't be afraid to show your personality, laugh if it's appropriate, smile, make eye contact, welcome the opportunity to verbally prove yourself, be someone that they want to be around for the next three years and someone they can see getting along with patients. If it is a group interview, don't get ruffled if someone else totally nails a question or says what you wanted to say. If you're in a waiting area with other candidates, strike up a conversation with them - try to not think of them as competition. It'll also sort of warm you up for the interview and shake some nerves out! My faculty says the ones that are talkative with each other tend to interview best, so don't be shy!
If it helps to organize your thoughts - make a quick list of what your strengths are, awesome opportunities you've had, times you really connected with a patient or coworker or another student...you don't want to mess up an easy question like "why should we accept you" and you forget every amazing thing you've ever done (like the way I did.....lol I still got accepted though).
And dress professionally. Every once in awhile I see candidates wearing jeans and a nice top and I can't help but scratch my head.
Remember, they already like you - that's why they selected you for an interview.
Good luck!
