I am a long time interviewer for a highly selective school. You should enjoy the meeting and use it to demonstrate your curiosity and learn more about the school. Be friendly and confident and open to hearing about all experiences even if they were long ago. Alumni interviewers are volunteers who love their university, so ask thoughtful questions and show your interest. Also, I never recommend looking up your interviewer prior to the meeting. It’s not about them, and they deserve some privacy.