I really would like to go to Japan after high school, but I know that it isn't really an 'welcome gaijin' place. Of course, I could teach English, which is convenient because teaching is my passion...well, next to the Japanese culture :P.

Who has experience with this and how did you like it?

Oh yeah, another option would be for me to work at a school on an American base. Would that require that I live on base as a citizen? Or would I have the freedom to live wherever? And if I applied for Japanese citizenship, would that end the job for me?
to maybe???
i didn't mean that they don't welcome foreigners in, i was just saying that its hard to live there
to the last two:
um, i'm aware I'm in high school
i'm also aware that to teach anywhere would require a college degree, so thanks for not answering my question.

No job even teaching English for stranger who is only high school grad in Japan is available because you have nothing qualification and/or experience.

Working on base doesn't make anything for you to eliminate to be able to apply for Japanese citizenship.

You need a four year degree to work in Japan. You also need a work visa. And to get the work visa you need a job offer before you get there. If you're fresh out of high school, there will be nothing available for you. Sorry, you just can't apply for citizenship, That takes years....Even if you marry a Japanese, becoming a citizen will take at least 5 years or more...
I think it would be a good idea to learn more about Japan and her culture before you decide you want to live there.
EDIT: Americans are NOT allowed the working holiday status.

You will not be able to apply for Japanese citizenship until AFTER you have lived gainfully employed in Japan for 10 years.
If you work at a school on an American base, I would imagine that you are part of the US Forces, in which case you would be required by the AMERICAN, not Japanese government to live on base.
Your statement 'it isn't really an 'welcome gaijin' place.' is NOT true in the least. I've been there 4 times,love it, and am always treated very well. Of course, if you have a negative stance before you even experience this culture, and behave like an idiot, they will not look kindly upon you, and won't welcome you as much. This is why many onsen upnorth have seen the need to barr American soldiers.
If you plan on getting a job in Japan,you need a work permit. This requires you to have a 4 year College or University degree in any subject, and you will have to have an agreement with an employer who will sponsor you.
You can however, apply for a working holiday visa, which allows you to work up to 2 years as assistant teacher or teacher. You will still need the degree, though.
If you want to try teaching in Japan, apply for the JET program.

You can't do any of this because you haven't been to college. You also can't just apply for citizenship, that's not how it works, it's a long and hard process. You need to marry a native Japanese or work there for 5 years legally and show that you're worth keeping around.

Good question, I'd like to know that myself!

I think there are a number of websites you can go to, which advertise English Language schools .

Good luck !