I'm staying with my wife's family at the moment, which means that I have to speak and listen to a lot of French. I've been doing this for several years now, and have recently got to the point where I feel comfortable reading at least some novels in French (I don't understand every word, but if the novel doesn't depend too much on florid descriptive passages or somewhat technical jargon, as is the case with several detective novels, for example, then I find it OK), so I'm doing that in order to try to improve my level of comprehension. It's hard to tell to what extent this is working, but I think the answer is non-zero.
From time to time, I realize that a word I don't understand has come up often enough that it would be very useful to understand it. An obvious thing to do in this situation is to look the word up in a dictionary, but that has the drawback that you just see a bare definition. To fix a word in your mind properly, what you really want is to understand it a few times in context. So when I've done that in the past, I've had to hope that I'll be lucky and that it will come up a few times before I've forgotten what it means, so that that fixing process can take place.
Recently, I've found a website that makes things much easier. It gives you not just the word but a large number of examples of the word in different sentences, all taken from the real world and translated idiomatically. How the database has been created I'm not sure, but I've found it a great tool. Just now I looked up the word "écart", which I'd been hearing. It turns out to mean "gap" or "discrepancy" and is used when one might say something like "There is a big gap between the government's promises in its manifesto and what it has actually done since being elected." Another word I looked up recently is "décalé", which means something like "shifted" or "displaced", but can also be used metaphorically to mean "quirky". But again, one understands the meaning far better after reading thirty examples of the word's use. So this is going to be my French/English dictionary of choice from now on (or until I find an even better one).