Preparations moving to Japan

I'm currently a 20 year old college student. I plan to move to Japan for at least a year when I'm 22-23. To either Tokyo or Osaka. I just wanted to ask for advice about what I should be doing to prepare for my eventual trip. I've already begun saving and taking a language class. There are a few things that I really want to know, like:

-How much money should I save up?
-Who should I talk to to make arrangements?
-Which city would be preferable to live in?
-What is the first thing I should do before anything else?

I'll take any advice that anyone can give.

It depends on what you plan to do in Japan, i.e. work or study, etc.

If you plan to work, the first things I would look into is finding an employer and getting informed about visas:
http://www.japan-guide.com/e/e2221.html

Talk to your nearest Japanese Embassy or Consulate for more visa advice.

I mostly plan to work while I'm there.