I hate to say this, and I hope it isn’t a general rule, in spite of making A’s in college French, I didn’t and probably couldn’t learn it enough to converse and think in it until I lived 24/7 with someone who didn’t speak English. It was hard, I kept a dictionary by the bed, but classes and vocabulary lists were never going to get me there.

The constant challenge to think and speak in the target language, and removing the temptation to revert to your native language, was irreplaceable in my case. Otherwise I would suggest reading anything in French – every day – that interests you and looking up every word and construction you don’t know as many times as it takes to remember it.