Immersion or bust.
I started learning Spanish in 8th grade. I took Spanish courses throughout high school and even earned A's. Unfortunately most of the information went in one ear and out the other. By the time I started college I barely remembered how to form a complete sentence in Spanish.
I had always heard that the best way to learn a language was to immerse yourself in a country and culture where that language is spoken.
This couldn't be more true. I first studied in Spain in the summer of 2007. I learned more in my three weeks there then I did in four years of high school language courses.
I was hooked and wanted to truly become fluent. I studied in Costa Rica the following summer for three months and finally solidified the skills I had been working on for so long. Studying abroad, and learning Spanish in an immersion environment is an unrivaled experience for serious learners and casual explorers alike. It's also pretty nice to go to school a block from the beach in Costa Rica and take surf lessons between classes.
If you have been thinking about it, now is the time.