This depends on what you mean by fluent, but the best way to increase your level is to have a balanced approach that targets both receptive skills (reading, listening) and productive skills (speaking, writing). This engages your mind and body more completely than focusing on one thing. Even if your goal is to speak fluently, learning to write well can help you to understand word placement and can give you opportunity to thinking more fluently (we normally write more slowly than we speak, which allows us more time to think without it seeming awkward).
If your English is already at a decent level, you are probably aware of the aspect that gives you the most trouble. (For me, it is listening.) You might need to focus on that aspect with a language partner or tutor.
I would suggest talking to natives daily, as well.