The first prospective student is scheduled to arrive in just a few hours. Let the partying commence, or something like that.
It's always hard to figure out how to interact with prospectives. We do interviews. Out of the 12 visitors, somewhere between a third and a half will actually return in the fall (based on recent entering class sizes of 3 to 6). My input may or may not be useful (i.e., used) when the faculty decide who to accept. Based on recent ruminations about my own acceptance decisions, my biggest role is in helping the prospectives figure out what they will decide if they do get accepted. I can either scare them away or share the misery.
Not that I intend to frighten them off, or am that miserable in graduate school. I intend to be honest, should my opinion be solicited. Not long ago, someone asked if I would still come to this school if I were making the decision now. There is no straight answer for this question. Things have obviously not been perfect. There have been times where the alternative - a professor in the middle of switching schools, where the first year would have been taken up by lab building - seems preferable. But then, I could never really know what that advising relationship or research would have been like. I don't like being so far away from my family, but I prefer the city I live in to the closer-but-blah alternative. I don't regret the decision I made, and am in general quite happy with the way things turned out.
On the other hand, I have a lot of pointers to prospective students. I've heard tell of one particular advisor who does not meet regularly with his students. One was okay with this; one hated it and switched advisors; one asked for regular meetings. It's things like this, specific to the advisor to the department, that would have been useful to know a few years ago. It's always good to have some idea about what you're getting into.