If you practice the questions on the USC interview database on SDN, I think you will do fine. It is a good idea to analyze your responses: where can I explain more, is there a confusing point, how will the interviewer follow up on my response, etc.
The best advice I can give you for interview day is practice with the pharmacy students in the lobby - get warmed up. You should sit down in one of the chairs and just chat with people and the pharmacy students. When the interview starts, it'll just be like that! Also, when you are being walked to the interview room, don't walk too fast or you'll work yourself up - take it slow.
The USC interview process was great compared to the others I went to. The students were approachable, and the atmosphere was comfortable. Jim, the admissions dean, is a fantastic speaker, and he will make you feel less nervous about the whole process.
The important thing to realize during an interview is that you don't have to rush. It's not always necessary to instantly answer all the questions. You can take some time to think about it. Don't feel like you need to respond quickly or that there is a time limit. This was one of the things I wished I realized sooner.
Good luck with your interview!
