thesterlinggirl,
First things first...congratulations on your interview!
Second, do not be nervous...be prepared.
While this may or may not work for you, I approached the medical school interview process like an employment interview. I had a strong desire to attend MSUCOM (e.g., my future workplace) and as such, I learned as much about Osteopathic medicine and MSUCOM's program (e.g., my future vocation/employer) as possible. I found SDN, AOA, & MSUCOM's websites full of useful information. From this information, I formulated questions specific to MSUCOM's program and diversity of class, as well as the practice of Osteopathic medicine in/out of the state of Michigan.
Moreover, I tried to maintain a sense of calm reflection during the interview process; i.e., I realized that being invited to an interview was a huge step in the medical school process, an accomplishment of which I should be humbly proud. I also brought this calm reflection into my interview. While I prepared for the "why D.O.?", "tell me about yourself.", "why MSUCOM?", and "why do you want do be a doctor?" questions, I also tried to anticipate the myriad of ethical / moral questions which may or may not be asked. What I realized during this preparatory stage was that I did not want to 'script' my answers nor did I want to provide rote/regurgitated information. This was my opportunity for the interviewer to get to know who I am and not my representative. I keep my answers succinct, candid, and sincere; yet conversational.
Remind yourself of why you have chosen this path (vocation) in life. This was very easy for me, as the culmination of my life's threads have been woven through the common fabric of helping my fellow man. Albeit clich?, it is the simple truth.
Perhaps the best advice I can provide is...remain calm and humble. This is only one part of your 'applicant profile' and I am sure that if you remain true to yourself you will do wonderfully. In all honesty, my interview was a very stress-free and pleasant experience.
Again, congratulations and best wishes during your interview.