Some programs will let you know ahead of time what faculty member will be interviewing you. If this is the case, look over their CV and read a few of their published articles. You can talk about their research, or their career path (how they ended up where they did, etc). Even if you don't know ahead of time, you can still ask the interviewer about themselves. Once they stop grilling you with the mandatory questions it can become more of a two-way conversation.
It is sometimes easier and more likely that you will have questions about the program. There are generally info sessions prior to the one-on-one, so you can ask for clarification about some aspect of the program. I've asked questions about service learning, international programs, scholarship opportunities, etc. Anything that sets that school apart from another PT program. One school had a larger class size, so I asked my interview about how they ensure the quality of education is the same.
It's my personal opinion that you should stay away from questions about the PT profession. Not that there aren't relevant questions, but to me, it could seem like you aren't that knowledgeable about PT. If you are interviewing at a program, you have hopefully already decided that PT is the career for you and you should have enough basic information. But like I said, that's just my opinion. I think questions like "what's your favorite thing about being a PT" or "what is your opinion on -insert PT topic-?" are questions you should be asking the PTs you shadow prior to attending an interview.
If you are attending a whole-day interview session or open house, there will be plenty of opportunities to ask questions outside of the one-on-one. Remember, at most programs, this is your chance to interview them and see if it is the right place for you. They should be trying to impress you just as much as you are trying to impress them.
