Here's a tip from someone who has relatives in Japan, and a high school buddy in Tokyo..
DONT WISH FOR TOKYO!!!
It's HELLA expensive. Many of the things we take for granted here int he states are VERY costly over there, so bring shit with you if you can like Catsup, Toilet paper, your favorite type of chips, favorite US candy, etc... If you are the shady type.. bring a bunch of bluejeans from goodwill over and then sell them for 100 bucks a piece (you didnt hear that from me though
).
How good is your Nihongo? Can you read and write Kana? Have you spent any time in really small cities? Sometimes they put you in some little farming community and you may be the only gaijin around so you might get (and when i say "might" i mean..you
will get) some stares. Just have fun, and dont overpack.. because i hear they make you schlep your luggage to and from when you get to/leave orientation. Good luck dude.. and if you need to talk, or have any more ?'s PM me. I haven't been to Japan since I was a kid, but im a fountain of information about the subject.
Some sites to check out:
http://www.jetprogramme.org/e/index.html
http://montreal.jetaa.ca/
http://jin.jcic.or.jp/
http://www.mofa.go.jp/