If there is no open house you should be able to do a campus visit and meet with admissions and a student ambassador.
Things to do:
-talk to the people who decide your fate. show interest, let them know your name, ask intelligent questions.
-discuss the future of the program. any changes in curriculum? class size?
-take a look at the criteria list in the FAQ. If anything on that list is a deal breaker then you should discuss that and be sure the school meets your needs (not the best example: you want to go to this school because of a link to a residency otherwise other schools are just as good. Is the residency still an affiliate and not closing/decreasing size of program)
-discuss the system for getting an interview acceptance. some schools don't like talking about this so careful here. Is it a point system? are there screens? 😀
I found that as I researched a school and received answer to my questions more questions would pop up. So research your school before going to the open house. this will also help avoid questions that could easily be answered from the school website.