Completely emerge yourself in that culture, language, or country. By that I mean read & write only in that language(newspapers,internet etc...) which you want to learn, watch TV only in that language etc.. hang out with people from language, country. If you are not willing to move to the country or countries of that particular language, then you must surround yourself with it to the point where you have no choice but to learn it. That's how I learned spanish!
