Firstly, I’d like to point out a fascinating thread over at Reddit discussing this exact question that has a lot of interesting responses and turned into a great discussion: How did you become fluent in another language?
Secondly, if you haven’t joined the language-learning subreddit on that site, you should, it’s worth joining just for that alone (and the people on reddit are awesome for the most part, by the way): /r/LanguageLearning
Thirdly, if YOU have ever learned another language to fluency (we’ll say “conversational fluency”, basically just to the point where you could readily converse with the natives about whatever) then I’d like to hear from you in the comments about how you managed to do that!
I learned to speak conversational Spanish in six months using TV shows, movies, and even comics: I then wrote a book on how you can, too
I have a whole method and a book I wrote about it called The Telenovela Method where I teach you how to learn Spanish from popular media like TV shows, movies, music, books, etc. that you can all find online for free. It was the #1 new release in the Spanish Language Instruction section on Amazon for nearly a month after it came out and currently has 17 reviews there with a 4.9/5 stars average. It's available for $7.99-$9.99 for the e-book version depending on who you buy it from (Kindle version on Amazon is now $7.99) and $16.99 for the paperback (occasionally a bit cheaper, again, depending on who you buy it from).
It's currently available in both e-book and paperback from: