Spanish is my second language. I'm currently taking my fourth year of it in school. I would say that although in-class lessons have helped a lot, it helps even more to use it outside of the classroom (speaking, listening, writing...).
I have plenty of opportunities to use it. About twenty percent of the population in my town speaks Spanish as their first language; there is a sizable community of Mexican immigrants here. Although the majority of the immigrant-students catch onto English quick, the adults generally have a tougher time.
Also, I have a question for those here who know multiple languages. When you dream, do you dream only in a particular language, or does it change from time to time? I've had some Spanish dreams, but they occur very, very rarely.