Promotion on Youtube? How?

Hey there,
I come again with newbie questions to the great BHW in my journey to making money online.

Today's questions is:
I have a startup movie streaming website. If i look at other successful movie streaming websites, I see a lot of their referral traffic comes from Youtube (and I'm talking about millions in traffic). How is that done exactly? They make their own channels on youtube and post content every day with their site link in the description? They post their link in millions of comments? Video ads?

any luck with your search ?

Google for their links to find videos. Actually, it looks like really easy to drive traffic from YT.
Upload parts from movies to your channel like 'Best parts of Matrix/Harry Potter', "Fight lord of the rings" etc. There are tons of famous movies/tv series.