I am currently a first year student. Here are some of the things I remember from last year...
First of all, try your best to visit as many school as you can or at least your the schools at the top of your list. I felt that this helped my schools put a face to a name. Also, I used some of what I learned during my visits in my personal statement so that I could personalize it to that specific school.
Treat any visit it like an interview. So, dress up! Some schools you may do a lot of walking so be a little weary about wearing heels (I made that mistake last year). If it is a one-on-one visit, I would expect that they will ask you more questions. For group visits, they may not ask you any questions at all. DEFINITELY be able to answer the questions "Why audiology?". Try to avoid the typical "I liked my audiology class in undergrad". I don't really remember any of my interviews getting to technical with their questions so I wouldn't worry too much about sounding dumb. It probably wouldn't be a bad idea to quickly look over your old audiology notes, if you have them. They may ask you why you are interested in their school particularly. Try to do your online research for each school... look to see what the professors are doing their research on or specialties of the program. Also, they may ask what type of audiologist you want to become. I still have no idea and I don't think many of my classmates have much of a clue either so don't feel too bad if you aren't 100% sure.
Some of the questions I asked them were about their clinical placements. I really wanted to know when students started clinic and what sorts of placements students are put into throughout the four years. Also, you may want to ask about 4th year placements. UC Boulder pretty much wanted students to stay in Colorado while Ohio State told me not to plan on staying in Ohio for my 4th year. If you are interested in research, you may want to ask about research opportunities. I also asked some questions regarding GRE scores, # of applicants, and what the school particularly looks for in a personal statement.
Earresponsible- I would suggest waiting until next summer or fall to visit so that they remember who you are and the schools will be fresh in your mind while you are applying. If you are really interested, maybe try contacting them and having them send you information about the school or program. However, this is just my opinion.
I hope this helps! Good luck!