My eldest brother just took a trip with his Japanese language class to Tokyo. Thing was, it was NOT a school sponsored trip. He probably spent close to $4000 USD. He loved it. Two things he recommends you ABSOLUTELY take with you:
Title: The Kodansha Kanji Learner's Dictionary
ISBN: 978-4-7700-2855-6
Price: ¥3900 (about $35.00)
Reason: The very best Kanji dictionary ever published in a portable size.
Title: "Langenscheidt Pocket Dictionary / Japanese"
ISBN: 1-58573-038-6
Price: $13.95
Reason: The most compact, practical set of useful Japanese<->English vocabulary you can carry.
(copy/pasted from an email he sent me)
I haven't myself been to Japan, and my current college doesn't seem to be offering a trip this coming year (or at least this coming semester, anyway). I do intend to go someday, though~ ^_^ !!!
@Thatsmypocket
A couple things I constantly hear people saying to do before going to Japan:
Learn how to use Hashi (chopsticks)! ... !!!!!!!!!11one!
Get a small inventory of Japanese phrases stuck in your head (if you don't intend to learn the language, anyway).
Figure out a budget for spending while you're there.
If you're going to stay with a host-family, bring a gift or two from your home country.
Hope some of that helps you at least a little bit!