We just had a cadre of students who have been accepted to our graduate program visit our department; it's a way for us to try to recruit them, and a way for them to try to decide where to go for graduate school. The power relations are unusual: the visitors are treated like royalty, and, moreover, the offer of admission has already been extended, so there's no way to screw that up. However, there are many ways one can make a bad impression on these visits. To wit:
1. Do not tell the chair of the department right off the bat that you've come just for the free trip and food. (A student in recent memory did this, but wound up accepting our offer in the end... That was fun.)
2. Do not say a faculty member anything resembling the following, "You work [in area x]? Why? Don't you know that philosohy has moved beyond that?"
3. Do not say to a faculty member, "I read your book on [x]. It was good introductory material."
4. Do not say to the Director of Graduate Studies anything resembling the following, "I'll never take any courses with you, and have no interest in [your area of research], so is there any way we can arrange for someone else to be my DGS?" (I heard this one third-hand; on only a highly charitable interpretation was the student mistaken about what a DGS is....)
5. Do not boast over dinner that you have "already written" your dissertation, and are simply "going through the motions" until it's time to submit it.
It should be emphasized that once you accept an offer and enter a program, the power shifts back to its more usual dynamic, to the great advantage of the faculty. When goodies are being doled out, or when special opportunities arise, the ones who made a bad impression are often off the radar.
Good luck to all in choosing a program.