YouTube — second largest search after Google.
1. Keyword research
TubeBuddy, VidIQ, auto-complete.
2. Title
50-60 chars. Keyword first.
3. Description
First 2 sentences show in search.
4. Tags
20-30, main keyword first.
5. Thumbnail
60% of CTR from thumbnail.
6. Watch time
First 15 seconds critical.