An interview is mainly a conversation. The interviewer is interested in you as a prospective student and the way in which you respond to the questions, not in asking trick questions. Most questions will be the easy common ones concerning why you want to go to that institution, what your goals are, and your interests. Often there is a reflective question such as "What was your research paper in senior English and what did you discover through the project?" Be relaxed and confident. Follow the same steps you would for the night before a big test: get plenty of rest, have everything you need laid out and ready to the night before, give yourself plenty of time to get to the appointment. A smile and good eye contact will help you make a good impression.