First of all, congrats. Studying abroad is a great experience for most people and I remember those times as some of the best in my life.
The best plan is to look at what you use on a daily basis and decide what's easier to get on an as-need basis when you're there. When I studied abroad, I brought so much miscellaneous crap I didn't need (like an umbrella...wasted space when they're 400 yen) or hardly used (like a trenchcoat I didn't use because I wanted a P-coat anyways).
The things I found absolutely necessary, other than clothes and a sturdy bag: mp3 player/music, camera, rechargeable batteries, dictionary (bought an electronic dictionary over there), and a willingness to put myself out there and make mistakes.
Have fun and be sure to post any more specific questions you might have.