Make sure you're logged into your favorite social networking service, first. Once you're logged in, and you've pressed the Share button, pick your favorite social networking or microblogging service from the available options. YouTube will automatically create a post for you that lets you share your video with your favorite service, including Facebook, Twitter, MySpace, Orkut, and Bebo, and Hi5.
Your post will open in a new window, so you can share with more than one site if you'd like. You can customize your link with a caption or introduction. The preview and appearance will depend on the service you use and how they handle YouTube videos.
