I did fail to mention one other annotation you can add. At the end of your video you can add an annotation to your website, another demo video, etc. Just slide the annotation box to the end...and enter the correct link (a video link, page link, etc.).
Now, there are a few things you can do to your YouTube channel to enhance your marketing.
First off, in the description of your video place the URL to your website. It should include the full HTML (http://www.mysite.com). That will make it clickable.
Now, click your name at the top left corner of your channel page. Now in the top center you'll see the word "About". Click that and now you can add:
- A description of your site
- Add a link to your webpage
- Add links up to 4 other social media (sorry, LinkedIn isn't there)
Now your Video channel has all your links as well. I'm certain doing so will enhance your SEO.