Questions to ask on prospectives' weekend - waitlisted

[Nothingtown]

Hey all! I received a notification yesterday that I'm on the short waitlist for UNC Chapel Hill's Philosophy PhD program. It sounds like I have a reasonable chance of getting in, and they've invited me to their Prospectives' Weekend (which immediately follows the other one I'm going to at Baylor, so it's going to be a big weekend for me)! I was to use this weekend to get to know the department, obviously, but I'd also like to make a good impression, as it may make a difference in getting off the waitlist. 

I've read some well-thought out lists here of good questions to ask grad students. Are there good ones to ask the professors as well? Any questions to specifically avoid? Does anyone else have experience going to a weekend like this while waitlisted? 

People who've been before--any do's and don'ts you'd like to recommend, or general tips?