How to make sure YouTube video plays in HD

Simply add '&hd=1' to the end of your URL.

Say you want to share the following video, but want to make sure it plays in HD.

Original URL: 

http://www.youtube.com/watch?v=hSl3jcR4zBo

HD URL:

http://www.youtube.com/watch?v=hSl3jcR4zBo&hd=1