It all depends on your goal. If your main goal is to understand and speak, then videos, TV, and children’s shows are a great help. If your goal is to master writing and grammar, then you need to take lessons with a real-life teacher!
Here is a useful link 
From what I’ve seen, every learner is different and learns in a different way. I found that trying to watch tv, and especially modern films, was as useless as it was dispiriting. The only thing that was the slightest help was programmes like Meilleur Boulangerie and Tout le Monde Veut Prendre Sa Place, because of the degree of repetition.
There really is no substitute for drilling grammar, reading parallel texts (or reading a novel in French on an e-reader so that you can have immediate translation of words, phrases, sentences) and daily Journal en Français Facile; then moving to France and getting stuck in, including twice-weekly church meetings with non-English speakers.
And what worked for me is unlikely to work for the next person (especially the last point!) but is, I hope, encouraging because it illustrates how different we are.
I think it depends how one naturally learns and one size does not fit all. I have a friend who learnt reading Paris Match. Another who read policiers. OH worked through A level grammar books with his teacher (which was fine for grammar but useless when it came to hearing and speaking)
My way of learning was talking: to my teacher, to people in shops, to the doctor’s receptionist, to French members of our photo club.
It is easier to begin with if one controls the subject. So a conversation with the doctor’s receptionist is quite straightforward - known topic, known vocabulary. Where it all goes pear shaped is in an environment like the photo club where several people are gossiping at once and one has no idea whatsoever what they are talking about.
It does get easier. Then one peaks, and it gets harder again. 
My breakthrough many years back was completely loosing it with a vendeuse in Galeries Lafayette. It somehow triggered my neurones into a new pattern that could process French.
I recommend it as a technique 
I discovered I remembered more of my O level German than I realised when a toilet attendant at Frankfurt (?) station was banging on the door and yelling at me to come out because someone had held the door open for me and I’d not put any money in.
Not sure if I’d recommend it but I got a French girl pregnant and her parents didn’t speak a word of English.
…Perhaps just as well then, Gareth
I learned Italian by reading my Italian friend’s women’s magazines until I understood them. I’m told I speak it quite well but never did grammar so feel vulnerable.
But I do think straight into Italian when I’m in Italy - other languages I studied the grammar of are less spontaneous. Including French. But Jane_Jones is right - if you “lose it” with someone that helps . Customer service in France offers many frustrating opportunities as French thinking is so different from Anglo thinking and there it comes out.
I had a vasectomy, so that’s probably not going to work (not sure it would be an acceptable explanation to my wife either).
Worked/works for me too…
It’s an ongoing thing.. from everyday stuff where I’ll smile and use my best French to ask a fellow-shopper for help/advice re the product we might both be looking at on the shelf… to more involved situations… and every time I pick up new words/phrases. 
eg: this weekend someone’s dog was ill and a Vet was needed and I was asked to make contact/ help… sufficient to say that after many phone calls and finally talking face to face with a Vet… my French vocabulary has greatly improved in the doggy area 
I think there is “learn” and “get by in”. The latter is reasonably achievable, the former, I believe, for very able and very serious students. I learnt Spanish and French at school, about 65 years ago, going on to university. I go to France and Spain and eavesdrop conversations of which I understand hardly anything. Most languages have so much slang and unusual references that following them is very hard work. I’m not sure of the best way to learn, I don’t see how you can learn to speak by reading, and probably vice versa. As others have said, we all learn in different ways. Half the battle is knowing your way.
Don’t let yourself feel vulnerable ( yes, I know.. easy to say but…)
I only did 2 out of 4 years in French at my school (took GCE early and passed) and have forgotten what little grammar I would have been taught way back then in the Dark Ages.
I can read in French and by working at reading News etc every day… I have reminded myself how the adjective goes after the noun rather than in front (?)… blah blah blah all that stuff … but that’s about it. There’s not a hope of me actually having a conversation, speaking any sort of convoluted sentence.. but who cares. Short sentences are better anyway…
I was explaining (in French) to a couple of French visitors that I find Le and La a huge problem and they both laughed. I mentioned that I’d been advised to speak fast and swallow/mumble anything I wasn’t sure of.. " Yep… most folk will always understand" is more or less what they said. 
When we first started visiting France, I would scribble down words I saw on adverts/signs/notices and look 'em up later to check they actually meant what I thought they did…
Also, if I didn’t understand a shop assistant or an official etc.. I’d ask them how “it” was written… looking at it helped me to understand/figure out the word/phrase I was hearing.
Also asking “them” to use another word/phrase works well. Eventually we will both understand …
For me, the mixture of reading and hearing.. is a bit like a recipe… hopefully it will taste good if it’s cooked correctly.
From most of the replies, people have learned what works for them. It’s probably not helpful to suggest that “my method” will work for anyone else.
It probably is a good idea (a) not to worry too much and (b) try various methods.
One small suggestion for improving vocabulary - if you don’t already do so, try turning on the device language option to French instead of English, in your phone, tablet, laptop etc. All the instructions, commands, layout etc will obviously now be in French, but it’s a stimulating, fairly easy way of learning and absorbing all the tech words that are now part of our everyday life.We certainly didn’t learn these words at school, as almost none of them existed at the time…
Conversation stopper…or starter, depending on your point of view
When I speak French, I pretend I am someone who can speak French. Sounds odd maybe, or even deceitful or self-delusional BUT it’s not something I do deliberately. It’s just something that sort of happens, my brain moves to a different place.
The advantage, I’ve deduced, is that I am more confident and that helps greatly. I don’t translate and I don’t plot my way in English and convert (I’m naturally lazy, translating is too much effort) I just speak. The result is I sound fluent to others (I prefer to say fluid rather than fluent) and I can rattle of sentences in French seemingly effortlessly without stumbling. Yes, I do come a cropper from time to time but it works well as a general rule.
I think confidence is a huge factor and we can all be confident by focusing on what we know rather than what we don’t know.
I’ve tried books and classes and duolingo and vidoes but they are all too abstract for me. I learn by listening to real live conversation and trusting in my brain to do it’s thing. Like puzzle solving, it’s engaging. It’s not at all passive but appreciating how my brain works and feeding it accordingly.
Just recently, I approached a couple of ladies sight-seeing in the village. It was a hot day and I asked if they knew that drinking water and toilet facilities were available just up the road…
Of course, I automatically spoke in French and we were well into a general chat about our local historic buildings etc etc , when one of them asked (more or less) “do I detect a little accent?”.
They were wondering if I was from Holland or Belgium. They explained that they recognised “something” in the way I spoke French, but couldn’t actually identify what that “something” was
Of course, I had to admit to not actually being French but they were surprised when I said I was English.
So, my French is (possibly) better than I thought
But you must have some basic knowledge in the first place surely. You can’t just “listen to conversations” and start speaking a foreign language.
You could be arrested for that Stella