I'm fluent in German, English. I'm living in Japan and am almost fluent in Japanese and quarter fluent in Korean. I also recently started Hungarian and Spanish. The most important part in my opinion is to live in a country that speaks the language you want to learn. You have to immerse yourself as much as possible with the culture and language. Also very important that you aren't afraid to try to use what you learned…
Only because...the textbook definition and the colloquial definition differ. I think generally when people say 'fluent' they mean 'native speaker level at reading, writing and speaking language X', whereas fluent actually means you can speak without hesitation on a range of topics.
Just a clarification, not an attack!
Edit: Plus, I wouldn't knock wordlists. I started trying to make wordlists only out of words I had some connection to, but you end up spending an inordinate amount of time making cards, and also then it's tempting to keep interrupting your reading to make new flashcards.
I am 'fluent' in mandarin, and use HSK6 wordlists as a base. I learn a bunch of random words and then suddenly, when I'm reading an article, there's the word I learned a month ago. I don't need to interrupt my reading flow, and the connection has been made. Sometimes at advanced levels, you won't see a word that often, so it's wasteful to see it once, make a flashcard, and then never have another chance to see the word in a real world context for another 6 months.