The quickest dirty hack is using Anki or another spaced repitition sytem program. If you download Anki you can get at the shared decks and there rea some very nice ones for German vocabulary.
For speaking/understanding speech I've heard great things about Pimsleur. Once you have the rudiments of the language listen to podcasts all the time.
Learn the grammar. You are unlikely to pick up more than the utter basics by osmosis. Good luck!
Anki is amazing on the desktop, but the iPhone app leaves something to be desired (note, I last tried it Dec 2010, so the app might have changed significantly since then).
If you want a large base of cards to start with and the same idea of learning (SRS/Spaced Repetition Software), I'd recommend one of the many excellent Quizlet iPhone apps[1]. I personally use Flashcards Deluxe by OrangeorApple[2].
You're welcome. The Volkshochschule have ridiculously cheap evening classes for all levels of German ability. In the unlikely event that you're at a loose end for weeks at a time the Integrationskurse are ~free. Google 'em for more info.
For speaking/understanding speech I've heard great things about Pimsleur. Once you have the rudiments of the language listen to podcasts all the time.
Learn the grammar. You are unlikely to pick up more than the utter basics by osmosis. Good luck!