How did you become fluent in your second (or third) language?

Could you tell me how you acquired your second or third language?

For example: how many years did it take you to achieve fluency? Did you start as a child, teenager, or adult? Were you around native speakers of the language? Did you live in a country where most people spoke your second language? Why did you decide to learn that particular language?

I’m particularly curious to know if any of you gained fluency without experiencing language immersion, but just with books, classes, cds, etc.

I’m an English as a Second Language teacher, but these days I’ve become interested in this topic on a more personal level. I’ve been thinking about my own study of Spanish and all of the factors that contribute to my current level of fluency…most notably—a serious boyfriend who is a native speaker of Spanish. You can imagine the increase in my motivation. ;)

So, what was it like for you to learn another language?