In general be able to talk about the classes you are taking, what you might want to major in, what teachers you like, what books you are reading now, what Extra curriculars you are doing, what of those you might want to continue into college, why you want to go to NYU, what got you interested in NYU.
They will ask you if you have any questions for them. If they are a student, you can ask them why they picked NYU over other colleges they were admitted to. What surprised them about NYU? What has been the best and worst part about living in NYC?