What would be the best way to further teach myself Spanish for fluency?

I took four years of Spanish in high school, but two years later, my grammar is pretty rusty, though I recall a lot of the vocab. I'm gonna take Spanish classes my last two years of college, but I know I won't become fluent with just that. What would be the best things for me to do to become fluent (I know it'll take a while). I don't know anyone who speaks Spanish, btw.