Hello Akimomo! In answer to your questions:
How to start: when you decided to go
I decided to go about a year before I actually went. I applied for an English teaching job through the JET program.
>> How did you find your job. Did you follow extra courses to get the desired job? What sorta jobs are available besides being an English teacher. (I ask this because it would influence any future studying)
Applied through JET. I didn't need extra courses, only a Bachelor's degree (four year degree). There are private english conversation companies as well, but most of them require a four year degree (some like TEFL or ESL experience or certifications). As for anything aside English teaching, it depends on your field of interest, but most jobs will require at least some communicative Japanese ability (if not fluency).
>> How easy/hard is it to find a job?
It's relatively easy to find an English teaching job while living in Japan. As for outside of Japan, finding English teaching jobs are the easiest. (Although some, like JET, are competitive).
>> How did you search for accommodation
My housing was taken care of, but there are plenty of websites out there that offer to help with housing. Finding housing in a bigger city like Tokyo, etc, is often easier than smaller cities. Especially without Japanese ability.
>> English teacher: what if the English language is not the native language? And what about other languages besides English?
If English is not your native language, then you have to prove you are fluent and capable of teaching it. Some companies are ok with this. (Some are not.) It is possible to teach other languages here, like Chinese, Spanish, French, etc... but it depends on the company.
Financial:
>> Living in Japan is expensive~from what i heard. Earlier experiences there do tell me that accommodation is expensive and getting around. What did you do in the beginning to get accommodation? What about finding a house/renting an apartment? Would you consider this the most difficult step?
My housing was taken care of, and subsidized. If you get an English teaching job, many companies offer teacher's housing. Otherwise, yes, accommodation is expensive. Finding an apartment on your own is difficult.
>> Social health care. How is this topic towards foreigners? What about pension?
Foreigners have to have health insurance. It's cheap, although sometimes a pain to find doctors who understand English (and will actually listen to you). Pension depends on the job you have and your employer.
Language:
>> I am now learning the Japanese language. I can get around quite well and my Japanese improves VERY quickly when using it active. Is this important in the procedure of getting a job/house/... in Japan?
Yes. See above.
Last but not least:
EXPERIENCES! I would love to hear how people start from scratch(or not?) in Japan. I have been there for a month, got to know Japanese people, have been to a Japanese school that teaches English to kids etc etc. I enjoyed this a lot!
I know this post is long, but i think this will also be very useful to others as this gives some sorta overview.
Thanks!
I was fortunate not to have to start from scratch, though I know some people who do. It is more difficult, but being able to speak Japanese (and having Japanese friends to help you) will go a long way! You'll need a work visa though, to stay, so it's best to locate a job so you'll be able to stay longer than the 90 days with a tourist visa.
Hope that helps, feel free to ask me more questions!