SEO for YouTube is largely the same as for a webpage. The basics are:
Use your main keyword in your video title.
Use your main keyword(s) in your video description.
Use your main keywords in your tags.
For using your videos to promote your website, make sure to use the full URL (example: http://www.yourwebsite.com
) in the description. Also put some kind of offer to direct people to your site for more information, a free bonus, etc. in the description, and in the video itself.
With regards to linking, you'll want to link to your video with keywords in the anchor text from as many different web pages as possible, including your website. You can link from forum and blog posts, online articles you've posted, and/or by using link-building services.