When should I change my major and what should I change it to?

I have applied to Arizona State University saying I wanted to study Pre-Vet but I changed my mind. I have already been accepted into the program but I want to do something else. When I graduate I want to become an english teacher in Japan. So my question is this:



a) When can I change my major and how do I do it?

b) Seeing as how I want to be an English teacher in Japan, what major should I take up that will allow me to become an English teacher in Japan?When should I change my major and what should I change it to?
this link should help



http://students.asu.edu/majors-other-stuWhen should I change my major and what should I change it to?
For fall, change your major ASAP



Obviously, can you speak Japanese to the level you could translate at the UN?



I would contact the Japanese for precise detail



http://search.yahoo.com/search?p=japanee