YouTube is already one of the best video services online and there are plenty of tricks to make it work for you. Some of the best ones, though, can be done purely from the URL bar.
You can:

• Repeat All or Part of a Video
• Download Any Video
• Bypass Regional Restrictions
• Jump to a Specific Time
• Disable Related Videos
• Skip to the Good Parts With the Wadsworth Constant

Full details of how to do it in this article from lifehacker: http://lifehacker.com/the-six-best-youtube-url-tricks-1422544868