What is the best way to learn Spanish?

Hey! I already speak French fluently and have some experience in learning Spanish, but I'm looking for a way to really learn it, so that I can go to South America and live there for a while. I know that the best way to learn would be to just go there, but the jobs I will be applying for require some level of fluency, so I need to be prepared beforehand. Any ideas? Some people have suggested watching movies and learning songs by heart. Has this worked for anyone?