"Hi, how are you?"
"Did you have a nice trip here?"
"What have you done while in town?"
"What do you like to do for fun?"
"What can I tell you about this program that dont already know?"
"What can I tell you about the city that you dont already know?"
"What can we do to get you to come to our program?"
These were the questions I was asked on the vast majority of my interviews. They are super laid back so dont sweat it. In fact, some interviews can get really boring and uncomfortable if you dont have an answer to the question "What can I tell you about this program that you dont already know?" So even if you have done research and know everything about the program or even if you have already asked 10 other people the same question that day, ask the interviewer. If you dont have any questions, often the interview will end quickly. They are mainly interested in presenting the program to you and making sure you are familiar with everything the program can offer. You may have one or two that actually have tough questions. I had one interviewer who pimped me on basic science aspects of my research during my interview. Just play it cool during the interview and blow it off afterwards because I think they are rare and they are just trying to get a rise out of you. Good luck!