They usually give it to you. They made it a point at my last interview to make sure I had their business cards. Very cool if you ask me. 😉
If not, you can always ask one of the admissions people at the front desk if they have their contact information. Or you can just ask them... but usually they'll give you everything without you asking, lol.
I just flat out asked them. Got all done and said, "do you guys have business cards or contact information I can grad from you." Got accepted to both places I interviewed so clearly it wasn't THAT rude.