@raymondli: Don't pay any attention to all these old school blokes who selectively forgot that they too were once the rookies of yesteryear. Aviation has an overarching tendency to inflate one's ego. When you make it to the top, try not to be the next bastard who needs fresh meat to impress.
Back to your question: as with any interview, do your research, come prepared and ask questions. You'll be no suspect under interrogation (do not act like one!) so see it as much as an opportunity to learn about who's on the opposite side of the table.
Doing your research and coming prepared means: general understanding of the aviation industry today and in years to come, having a rough idea of what to expect during your training and why that motivates you, why you chose to apply to this university (and program) over others, why you chose this path over going straight to a flight school. If you can spare them the cliché of having always dreamed of flying since day 1 for something more original, that'll do you justice.
Expect questions about how you imagine your career and possibly about the challenges looming in the aviation industry (to name a few: automation, over-regulation, ...). Also, if the program has a broader aviation focus than flying alone, tell them of any interest you may have in adjacent areas such as airline or airport management, aerospace engineering, etc.
What you can also do is get in touch with current students and tell them openly that you'll be interviewed and that you're looking for hints and tips.
Remember that it'll be a chance for your interviewers to assess you and see how much of a good fit you'll be.
Relax, breathe in and show them that you're a cool kid. At the end of the day it is expected that you'll be making mistakes in life. The path forward will be what you decide, not quite what you follow.
HTH