Jonathan Mendez's 7 Ways to Optimize Your YouTube Tags has a more detailed look at optimizing your YouTube videos. Here are some of the tips in summary.
- Use relevant tags to describe the video
- Use as many relevant tags as possible
- Think long tail searches when it comes to tags also
- Use adjectives
- Add category descriptive tags
- Most important tags should also match title and description of movie
- Don't use "and" "or" etc. words as tags