The quickest way to become fluent in a foreign language is to immerse yourself in that language. In other words, put yourself in an environment where only the foreign language is spoken. At first, you will probably find the experience very frustrating, but you will be surprised at how quickly you master the language. In a few months, you can learn more than you would have in years of traditional classes.
There are a couple of ways to go about language immersion. You can just visit a foreign country where the language you want to learn is spoken. This can be very intimidating, though, especially if you do not know any one there. If you decide to go this route, you should take a couple of language classes before the trip; this will help you from feeling completely lost in the first few weeks. Also be sure to bring a good English to foreign language dictionary.
If you want a little more support, you can enroll in a foreign language immersion program. You will still visit a foreign country, but you will also take regular classes to help you learn the language. This is an ideal situation, because it gives you all the benefits of immersion, but you also learn grammar rules and have some encouragement.
Classes
If you do not have the time or money to travel, you can simply take classes. Indeed, this is the most traditional, as well as the most common method. Some classes use the immersion technique; in these classes, the instructor will not speak English, and students are not supposed to speak English, either. Other classes are taught primarily in English, although as the students advance, less and less English will be used.
If your instructor is not a native speaker of the language you are learning, you may have a difficult time learning to speak with a good accent. In order to compensate for this, you can hire a native speaker to converse with you on a regular basis. If you are having a difficult time with the language, you could also have this person tutor you.