[samurai007]

Definitely buy yourself a good guidebook (I like Lonely Planet Japan myself) and take it with you. Read up on areas that sound interesting to you.

I'd recommend spending most of your time in the Kansai area, seeing Osaka, Kyoto, Nara, Koya-san, Himeji, etc. For food and shopping in Osaka, visit the Dotunburi area. Just look at the plastic food in the window, and pick a place that catches your eye... don't worry, I almost never had really bad food in Japan, even at tiny local places. So relax and explore!