This thread pops up once every couple years, it seems.
日常生活に必要なことばはできるけど・・・
I lived in Japan for one year between '05-'06, so I was able to pick up a good amount that year. I had a good head start than most Westerners since I'm Korean and Japanese language structure is pretty similar to Korean (i.e. default/flowy/optional subject-object-verb order, usage of particles, usage of kanji-derived nouns, etc.). Oh, and I studied the hell out of it when I was there too. But of course, it's been on a slide ever since I left.
And agreed that immersion's the way to go if someone's serious about learning the language, but that's no secret...
As a matter of fact, I have to start thinking about how I'm going to get my 1 1/2 year-old daughter to pick up half-decent Korean. She won't be able to do it in her current environment (in Western Australia, stay-at-home wife is Canadian). Might have to go back to Korea for a few years I guess...