IMHO buy youtube viwes from addmefast and also check tags in youtube
First of all, your video description must be clear and it has keywords in the tag. Also, you must receive more likes, shares, and subscriptions for your videos that what you want to get rank in Google. Even if your video shares virally in the social media and it has more links, then it may get rank in Google and will show on the first page of SERP.
I think from 800 to 1000 words is more than enough as your video description.How many words should have on descoption?