I do. Translate hentai / games. That's how I slowly got better at Japanese.

I do. I live in Tokyo, been here for almost 6 years. But My level is much lower than you'd expect for that amount of time (-.-;)

There's a pretty good language exchange website called lang-8. When you can form a few sentences, it's a good place to practise and get help.
Some free basic stuff to download from this school website.
Good spaced repetition program for learning vocabulary (used like flashcards) called anki Introduction to the langauge and good grammar reference here
I'll try and think of some more.

I failed Japanese in school. Just didn't know how to oppress the Chinese well enough.

Watch One Piece!

I know it sounds abit crazy but I've learned quite a few stuff this way.
Ofcourse this is just a secondary method and you can't master the language only by that :P

You applied to Japanese college.... yet you know hardly any Japanese. GG?

Get yourself some cat. :P

Rosetta Stone

There is no better Software to learn a language. It's really good and I recommend it!

Seriously, why would you apply for a college in a country who's language you don't speak, to finish a college you ened to speak more than well that language. Anyway doesn't that college has classes in english language? in my contry most of good colleges have english versions of all classes.

I know a little German

Watch current/recent Japanese movies/tv shows/anime with subtitles and learn a few new words each time, by looking them up on Google. Not the best way to learn fast, but it's fun and useful anyway.

Having studied Japanese at School and Uni, I can recommend Obento Workbooks and Wakatta! Workbooks for people just starting to learn Japanese. You could probs buy them form an online retailer. But any sort of extra curicular classes would help the most. Try and get your hands on a Lonely Planet Japanese phrasebook if you can too.

If you need a online dictionary: http://jisho.org/ is brilliant. I use it quite often.

For music, don't really worry too much about it when you're just starting to learn. Singers often distort the words too much for beginners.

I took some in college. I used a few different textbooks but Genki was the best, its used by San Francisco State. Reeeeally recommended.

EDIT: also this is my favorite pocket dictionary, it has the japanese words in english characters as well as hiragana/kanji :)

Arigato !

http://www.busuu.com

Besides everything that people said...

1. Watch a lot of dramas and anime, listen to japanese music, try to immerse yourself in it.
2. Have you tried YesJapan? It has lessons, but the best part of the site are the videos in my opinion. They're rather useful (and amusing).
3. Not sure if mixi.jp is still open to registration, but it used to be like a Japanese orkut. Chatting to people there can help you improve very fast once you start getting the hang of the basics, and the Japanese are usually pretty helpful and open to Brazilians. :)

Lang8 and similar sites are also cool. And DO USE ANKI, it's super useful. <3

Japanese people do

Rosetta stone just buy the Japanese pack only it should be fairly ceap its helpful i did 2 years of french back in high-school Rosetta helped me remember and learn new things.

I envy you. I've been crazy about the Japanese language and culture for a few years. I only know a handful of phrases, multiple ways to say "I'm going to kill you" (from all the anime I watch >.<), and the vowels. I can write less than 5 Hiragana and Katakana; I need to practice writing more. I'm using the application Human Japanese to help get me started on my path to learning the language. I would recommend you start with that before spending hundreds on Rosetta Stone.

The best way to learn a language is to immerse yourself in the language. I pretty much only listen to Japanese music and watch Japanese TV shows and anime. Two good TV shows are Kamen Rider and Super Sentai. A few good anime to check out are Katekyo Hitman REBORN!, Mirai Nikki, Sekirei, Highschool Of The Dead, Sora No Otoshimono, and Bleach.

Good luck in Japan! =]

some Japanese girl are hot.

Get Remembering the Kanji, and download Anki. On Anki, load up the RTK decks and a core6k deck (vocab), probably a kana deck as well if you can't read kana. Do both RTK and core6k - if you study fulltime, you'll easily end up knowing more kanji than students out of the school system, and you'll have basic vocab in the form of the 6k core words. As you're progressing through the decks, seek out untranslated material to conquer in your spare time - starting with shonen manga and moving on to stuff without furigana.
6 months is plenty, if you're willing to consistently put in the effort every day. At around 3 hours per day, 6 months got me through all 2000 kanji in RTK 1, as well as about 3000 word in core6k. Fulltime could even get you semi-fluent, provided you expose yourself to enough native material in parallel to mastering the vocab deck.
Check out AJATT and Reviewing the Kanji.

がんばってくださいね。

You don't even need to speak Japanese at the university that accepted you. All you need to do is get a translator and wallah! This is the exact same thing that Japanese and other immigrants are doing over in my area.

I learned basic battle orders from Shogun 2.

Nothing that'll be remotely practical or get me by in Japan, mind you.