Moving to Japan; need better language skills

So I recently found out that I will be moving to Japan sometime early next year for work related reasons.

I do speak a little Japanese and know enough to get around without too many problems (I hope)... But I have to be honest, I'm absolutely terrified. I've started Rosetta Stone and I'm up to Unit 5 on Level 1 and I have yet to learn something new/useful.

People who are native speakers of English and are now fluent in Japanese, how did you learn the language aside from going there?

I want to get A LOT better at it before I actually go. Not fluent, but I'd like to be able to hold a semi-decent conversation.

Also, I fucking suck at kanji. (I think I know somewhere between 200-250.) I'm reading Heisig, but is there anything else I could be doing for that?

I'm sorry, but I'm horrified of going to live somewhere for 2 years where I can't talk to people outside of work. (I know I had the option of declining, but it was too good of an opportunity to pass up)


tl;dr I'm moving to Japan in 6 months. How can I drastically improve my language skills before then?

Rosetta stone sucks seems to be the consensus.
I use anki (flashcard program) for kanji.
I've done a bit of pimsleur and it helps to repeat stuff even though I felt like a retard.
You can get a penpal to practice writing/talking.
Take classes? (probably not fast enough)
Use a grammar textbook/dictionary to look up grammar you don't get, but grammar is not the biggest hurdle.
I use http://www.alc.co.jp/ to get sentence examples. Once you get a hang of the basics, learning new idioms through example is pretty easy.

What kind of work are you going to be doing? In English or Japanese?