What’s the best way to learn a language? ?

> I was pretty good at German in school

Okay, so we can assume you know the basics already.

- watch german movies with good subtitles in your native language

- read german books with the help of a good dictionary. If you need to look up dozens of words per page, find an easier book

- listen to german-spoken radio (lots of countries have german broacasts on shortwave, internet or - if you are close enough - mediumwave) or spoken books

- you can use the german variety of yahoo!answers. It is called yahoo!clever

- you can watch german videos on youtube, but the automatic subtitles are horrible

- some details are explained elaborately on the youtube-channel donttrusttherabbit

Yes, go and live in Germany.  If you were pretty good at german in school, then you should have a good vocabulary and a basic speaking capability.  Now you would have to add character by interacting.  That was the best way for me to learn Spanish.  I lived it in Puerto Rico, got a girl friend who taught me how to speak better.    Real practice is the only way to improve...