I am teaching English in a Japanese high school in a mountain hot spring town, population: 35,000. AMA!
I'm not sure if this is interesting or not, but...
For those of you who knows such things, I'm currently doing the JET Programme, six months in. I live somewhere in the middle of nowhere.
Also, I'm from New Zealand, though I'm Asian (not Japanese) by birth. Ask away!
EDIT: Whoa, lots of questions! This is wonderful; gives me something to do during my breaks. But I has to go to sleep now. I'll reply tomorrow! Thanks everyone! :) [12:15am, Japan Time]
EDIT: Okay, FAQs.
Q: How much Japanese did you know before coming? How do I study?
A: I had JLPT N2. Japanese Level Proficiency Test. I studied it at high school and university. I don't really have any study tips because I was a lazy student, but this is an extremely good guide which will be able to help you out much more than I can: http://www.guidetojapanese.org/learn/. As for Kanji... sorry, I got a free pass on that since I spoke Mandarin (and sure, I was "lucky" - but I had to learn English from the ground up, too! And it's not like we get injected with magical Kanji knowledge at birth...)
Q: Questions about the JET Programme.
A: Eligibility and pay could be seen here: http://www.jetprogramme.org/. Don't worry about the fact they apparently favour Americans. If your country does it, you probably have a shot. No, you don't need to speak Japanese FOR THE JOB - but obviously it helps immensely. Any advice I could give would be non-American, and I think I'll start a thread in r/japan about my specific experiences with the structure of the programme later. There are plenty of other personal records you can scour from the internet, though. A few tips for aspiring JETs, though:
Write a killer essay. That's the first step to getting your foot in the door. Don't be a weeaboo. What can YOU contribute to the programme?
Have backups. I can't emphasize this enough. You are not guaranteed in.
JET is a job. It is not the best thing in the world nor is it the worst thing in the world. Research thoroughly. Make sure it's something you want to do. Don't glamorize it.
Make sure you can handle the stress of living overseas by yourself. It gets lonely sometimes.
Good luck, good luck, and good luck. I hope I see you here sometime!
EDIT: Also, also, JehuLove is my predecessor. He knows more about what I'm talking about than I do. Listen to him.