i had mentioned a personal tragedy in my SOP (to explain a gap in my resume) and they gave their condolences, which took me aback, simply because it was very nice and thoughtful, and i had been worried about including the experience in the first place (vs just not mentioning a huge gap in my resume).
read over articles and abstracts and bios of researchers i was especially interested in, read over bios of other profs (you are randomly assigned a prof to interview with, even if you mentioned a specific one in your SOP, so have a general idea of who everyone is). read over program info very throughly and made a list of questions to ask, and though of my answers to likely questions. i was overprepared.
What impressed you positively?
the students were smart, thoughtful, and happy, the prof and graduate i interviewed with were wonderful, school did 100% in the internship match, early clinical exp., lots of great externship experience -- if they could have funded me more it really would have been a contender, but i got full scholarships elsewhere. loved this program!
What impressed you negatively?
no tour of facilities, and i wish all the faculty had been available, so i could have at least chatted w/ my POI and got a feel for working with them -- which indicates that this is a more clinically oriented program than may have been right for me.
What did you wish you had known ahead of time?
nothing. loved the school, as good as better funded programs but ... short on $. knew about the funding shortage, would have gone into debt to attend if didn't get in to better funded, also quality programs).
What are your general comments?
relaxed, conversational. know about the program, think about your background, goals and your work as it relates to LIU, have a general idea of your research interests (and the work of the faculty) and then have fun chatting and meeting nice people. ask for a tour, or just poke around yourself.