Read the interview feedback. For each school I was interviewing for I made a pool of all the questions students were asked. I practiced all the questions and wrote out my initial thoughts. Do mock interviews and practice infront of a mirror. It may seem silly at first, but you will be surprised how important facial expressions and hand gestures are. Body language is very important at an interview. You have to be very confident in yourself and your responses.
May or may not help in an interview, but: If you're worried about the conversation dying out, always end every response with a question. This a good way to start developing rapport and keep the conversation alive.
Lastly, if you have the time, read the thread from last year for your school. You might not get any interview questions, but I know people talk about how things are set up, if there are any tours, and any info that you might need.
What I learned during the process is to keep your cool and have fun with it. It's nice to have an answer to all these questions, but if you do get one thats not here you still need to be able to keep calm and respond with well thought out answer. On that note, dont memorize any answers, you will sound like a robot and your interviewers will be able to tell that your answer is not natural. Just know what you want to talk about if a particular question is asked.
Keep in mind that more weight is placed on how you answer a question more than the answer itself. A big part of the interview is to see if an applicant has the ability to communicate effectively.
Dont go into the interview cold. Practice with friends and family so you can get used to the interview atmosphere, and learn how to think on the fly. All I can say really is to just relax, have fun, and practice.