There are 3 types of marketing for YouTube, and I'll try to dumb it down.
1. Big paid advertisements: Use Adwords, Facebook only if you got money to burn for your success.
2. Viral: Cute puppies doing cute things or even anchors walking off the talk show for kardashian's goes viral when posted to big fan pages or social groups, but hard to monetize.
3. Paid Ads with Black Hat Tactics: You utilize the buying of high quality retention views, likes, comments, subscribers, backlinks, social shares with paid advertising or endorsements to get your fan base.
Keyword in Title
Description optimized
Tags optimized
Views coming from related videos
views coming from keywords
views coming from subscribers
views coming from embedded sites
etc.
You'll get what I just said if you were to look at some of the major top channels for your niche.