[alanX]

You're well on the right track so far.

Basically...a condensed version of what you're trying to do:

Graduate high school.
Get a bachelor's degree at an accredited college.
(yes, you basically HAVE to have a bachelors to teach English)
Apply for English teaching jobs in Japan online.
They will provide all the visa mumbo-jumbo, and tell you where to live, where to teach, how much you'll make...etc.