I´m going to discuss some important topics about achieving fluency in a foreign langage. I´ll start by explaining when you know you´re already fluent. But many students would unwisely say this: I´ve finished my course, I have a diploma that says so. Sure, you may have finished your course, but there are some pretty crucial questions here! One of them is: from the time you finished it until today, have you kept in touch with the language on a daily basis? If your answer is negative, then I´m afraid you´re losing your fluency, especially if you finished that course a long time ago! Of course it doesn´t mean you have to start all over, but you should try to bring all that knowledge back by practicing and remembering it. Anyway, back to the definition of fluency! Being fluent does not mean you have to speak a foreign language just like you speak your mother language because this is fairly hard when you´re not living in a country that speaks that language most of the times. A language is a living thing and due to that, it´s bound to change from time to time, new words and expressions are created to keep up with the progress of mankind. Being fluent is mainly about: being able to read something and understanding most of the words and their meanings, being able to listen to different speakers (with different accents, different rhythm and speach speed) in many contexts and finally, being able to express yourself both in written and oral language, making as few mistakes as possible. In oral language, a fluent person must speak without hesitation, using correct grammar structures, with a good pronunciation (you don´t have to sound like a native, though) and showing you master idioms, current slangs and phrasal verbs. You don´t have to know specific or technical vocabulary, but you should show a great variety of words, from the most formal to the most informal. In a meeting, you would avoid using too many slangs, for instance, whereas in a chat with a friend you would´t talk as if he were the CEO of an important company you´re doing business with.
There is no such thing as a certain number of words a person must know to be regarded fluent, but the average estimated is 3000 words.
This is also something to bear in mind: the current stage of a student taking a course does not reflect the real level of proficiency he´s got. I have Intermediate students I regard as fluent and on the other hand, I have Advanced ones regarded as Basic. There are many things to take into account here: his/her difficulties, the school, the teacher, the method, his/her personal efforts, attendance in class, interest, use of the language outside the classroom context, etc. In a nutshell: never trust your certificate! Instead, rely on how much you think you kow the language and if you have doubts about it, ask your teacher (make sure he/she´ll give you a straight answer!).
To conclude, I´ll give a few tips to those who really want to climb their way to the summit of this steep rocky mountain. Never give up, try not to miss/ cancel many classes in a row unless it´s extremely necessary, avoid speaking your native language in class, always solve your doubts before the end of the class, take the learning process as a fun thing to do rather than an obligation, don´t miss an opportunity to use the language by reading, watching movies, series or tv or even talking to your friends (or to yourself!), be open to correction (don´t criticize your teacher for doing that, he/she knows best!), have a daily contact with it, if possible, travel to a country whose first language is the language you´re learning, learn how to use a monolingual dictionary, write down new words and try to use them to memorize faster, don´t stop studying (you never know everything!) and don´t be shy!