Four years of college Spanish wasn't enough to make me fluent, but it did help tremendously. It was moving here, getting a job in Spanish, and then of course having a native speaker boyfriend with whom I don't speak English. That's really the secret.
Took Spanish in college, learned very little, went to a one on one class in Houston, before visiting South America, and became conversant. Married an Argentine, and now doing well.
good poll - Other - (mixture of several) - studied in college, moved abroad and learned through immersion, and married an Argentine who would rather speak in Spanish.