Step 1
Get keywords with a high search volume, eg. cat music, running shoes.
Step 2
Use your keywords in title and description. Seo things...
Step 3 and here is the secret
Buy real comments and make sure they are using your keywords in them.
At that time I used microworkers, told them to write an appropriate comment for the video and MUST use some words or they're not gonna get paid.
With $10 (almost free) I've got 100 comments. The keywords for the video were in every comment.