I did this, and it's a terrific experience! I agree with most of what's previously been posted.
I didn't wear a suit, but rather went "business casual," and it turned out fine.
I brought a list of questions. I thanked myself for it, because I got a little nervous and had to look at the list. Having stuff on paper generally makes you look organized and well-prepared, so I don't think I seemed as nervous as I really was. The Dean seemed to think it was perfectly okay when I looked at my paper.
In fact, I brought a whole folder full of relevant papers (like the ones listed in previous posts). I ended up not needing some of the stuff, but it was great to be able not only to talk about some issues but to pull out a printout and say "hey, I was reading about this thing, and I noticed blah blah blah," instead of "well I've heard from somewhere, I think it was the school's website, uhh, that blah blah blah."
During our conversation, the dean actually offered to let me "shadow" a student for a day, and a few weeks later I did, and it's THE awesomest experience! Definitely don't pass it up!
One more thing I'd add: think really hard about a question you'd like to ask: not just any question, but one that will show your intelligence and your interest in the school. Ask something that requires some knowledge of the school. Show you've been doing your homework, both about the school and about the profession. Tailor your question to whether the dean is a Ph.D. or a D.D.S./D.M.D. (e.g., probably back off on any questions directly regarding clinical practice if they don't have a dental degree). Whenver I go to meet anybody for the first time, I try to do this, and it usually succeeds in making a good impression (plus the background research re school & profession is always really, really good for us to do anyway!).
Hope this maybe helps a little. Have a great time at your meeting! 👍