a little help please... (on Japanese food)

I'm doing a report for Japanese class. It's a group project of sorts, and my part of it is on "cheap ways to eat in Japan." I'm not sure how to start 'researching.' Anyone with firsthand knowledge of Japan who can suggest cheap ways or places to eat in Japan? Or, if not that, any pointers for good places to find info...?

-_-;;

My Spring break ended and I haven't accomplished a thing. I even forgot about Daylight Savings, and now I'm short an hour.