Every single day, my YouTube channel for Doggypedia has more than 24 hours of view time.
I attribute my success to two things:
1) The clickbaity thumbnails everyone does (easy)
2) Slamming new videos with as much referral traffic as quickly as possible (hard)
Any kind of referral traffic should work, as long as the traffic engages well with the video – Twitter, Facebook, Reddit, Email lists, embedding in existing webpages with traffic, etc.
Then wait a few months, just like with organic search.