I'm seriously considering the idea. first, i'm 20 years old and want to major in biology or world history/cultures (to be a social studies teacher)

i know you need at least 4 years of college to teach english but i've heard they started tightening up on who can or can't teach. if you've ever done this or in the process what kind of person are they looking for?

Go to www.aacircle.com.au
This site will answer many questions.
I taught there for 3 years.
All you need is a 3 year degree. I hope this site is helpful.

Also you can go to Dave's esl cafe

Go read some of the entries at http://www.gaijinsmash.net/ for an idea of what life is like over there. It's the blog of an American guy who has been teaching English in Japan for a few years now.

Yes, you need your bachelor's degree. At the moment, the English teaching market there is a little out-of-whack. The demand for lessons is still there, but NOVA, the largest English school (my prestigious former employer), went belly-up last year because of legal trouble. However, since you're still in school and have a couple years 'til you finish, it should be better by the time you're ready to go. I strongly suggest looking into the gov't sponsored teaching exchange program (JET), but you can also check out other private companies (AEON, ECC, and Geos are all reputable). It doesn't particularly matter what your major is, but you may have an easier time getting hired if it's more relevant (world cultures, perhaps). NOVA used to pay us an extra 20000 yen per month (about $200) for having a valid teaching certificate, but there were only two teachers at my school who had one.
For more details, check out my blog and/or email me.

(ps, Someone recommended gaijinsmash to you, which is an awesome blog, but Az doesn't actually teach anymore. He's a translator now, so his stories are all outside the classroom these days. He originally worked with the JET program.)

You can get your college degree in Japan WHILE teaching there(as a part time job). There are numerous Eikaiwa schools and I'm sure they will be happy to take you.It is expensive, but a student is allowed to work 28 hours a week. An average English lesson will go like 3000 yen, or at least 2500 yen/hour,and even if you don't work all these 28hours, you'll have about 225,000 yen a month, which is not bad, esp if you don't live in Tokyo or Osaka. You can afford to study there and there is also a tuition fee waver program in most public universities, plus numerous scholarships.
It will be hard to study and work, though. If you are ready to accept the hardships, then go ahead!

As long as you speak English and have a degree for a work visa.

They're tighting up in reducing benefits and pay. "Teaching" in Japan is not as great as it used to be, considering schools going into bankruptcy and closures. I put "teaching" in quotes because sometimes its just reading the company playbook without room for diversion, though depends on the company.

You want to be a Social Studies teacher in Japan?

If that's the case, then you have to go to a Japanese university like all other teachers there and get certified in Japan.

If you just want to teach English, then you can do that. The norm is to have a bachelor's degree to be able to teach in schools, and you will be an assistant teacher, not a full-fledged teacher.

You don't need a degree if you want to teach in other settings like eikaiwa (conversation schools), community centres, private one-on-one lessons, etc.

To teach English at university, you usually need a Masters degree. They'll pay you more if you have a PhD. You will be considered a real teacher, not just an assistant. Likely you will be teaching fairly basic English though, and probably not any other subjects.