Assuming things haven't changed, after you collect your name tag and packet, you'll be directed to one of the rooms to have some refreshments (OJ, coffee, fruit, doughnuts, etc) and meet other applicants. There will typically be other students (1st and 2nd yrs) present to poke and prod with any questions to have. Once all the applicants have arrived, Dr, Hayes, the dept chair, will usually speak to everyone. I believe you'll probably hear from Rik or Jean about financial related issues/questions as well. After that you'll be split into 3 groups. 1 group will be assigned to a faculty member to interview with. Those probably last anywhere from 20-30 minutes. The 2nd group will get a tour of the UM campus, and the 3rd group will get a tour of the dept which is basically just the 3rd/5th floor. I believe the dept has recently taken over some space on the 1st and 4th floors as well, so you may see what's going on there too. The groups will alternate until you've all interviewed, and gotten tours of the campus and the dept. Any down time in between is usually a good time to continue asking questions of the other students.
That's basically the gist of it. Hope that helps.
BTW, there is limited parking, so keep that in mind before you arrive. There are @ 10 spots behind the plumer bldg that are first come first serve to students who do not have a parking permits. Students usually have Fridays off (unless there is a planned elective course) so you have a good chance of getting one if you arrive early. Other that that, there is some metered parking around the building, and I believe you can still purchase daily passes at the Ponce de Leon parking garage to be able to park in a student parking lot.
Good luck.