Make sure your channel is already optimised following Youtube's guidelines. Then start link building, forums, blogs, web2.0.

Way to Optimize YouTube videos:

1. Content is the "All Powerful"
2. Tagging and Titles
3. Closed-Captioning
4. Call to Action!
5. Playlist URLs

Name the raw Vid file as one of your KWs, write a KW rich title, long and KW rich description and put the right tags.

Next, send in as many views as you can to your video, social bookmark it, share on social sites, get it embedded....the idea is to increase interaction and make it look that its a really "important" video.

That should rank your vid.

Hope that helps.

There are many ways to optimize a YouTube video-
1. You can submit your video on video sharing sites.
2. You can also do forums, blogs and bookmarking.

A lot of people overlook something that is very helpful with YouTube.

You have a big description box, fill it with heaps of relevant, unique content.