Also, you might want to bring something you can do subtly while you sit in the admission office, whether it's a magazine (I wouldn't recommend maxim or intouch, but something relatively normal would do) or a book or notes or whatever. Some interview days have quite a bit of downtime (ahem, Vanderbilt, ahem) in which you're sort of expected to "walk around" even when there's nowhere to really go.
Also, if you're the type who can't handle uncomfortable shoes (my feet are useless), bring a pair of comfortable shoes to wear during tours. Tour guides are usually students who have nothing to do with the admission process and they won't care (and you don't want to be wincing throughout your interview).
What else...be aware of your dietary restrictions and bring something along if you need it. I have a friend who has Celiac's disease and she brought gluten-free bars and there was another kid with Celiac's in her tour who didn't bring anything and was about to pass out from hypoglycemia mid-afternoon (she shared her bars). Don't be that kid.
Don't wear clothes so uncomfortable you're tugging them and fidgeting all day. There were some people at interviews who looked like they were wearing their parents' suits and they just looked SO uncomfortable. Wear it around for a day before the interview if it's a matter of getting used to it.
Don't wear strong perfume or cologne cause a lot of interview rooms are teeny and not ventilated.
Don't be the awkward kid in the waiting room who can't talk to people, but also don't be that weird kid that makes everyone introduce him/herself for no good reason (YOU'RE NOT GONNA REMEMBER 20 NAMES, KID).
Have questions! (lots and lots of questions).
Ok I think that's it. I don't know why I got into this so much, but hey, I'm on a roll!
