My suggestions : 

1) Video backgrounds make a website seem more lively and interactive to a user, but they are not very easy to pull off.

2) Figure out the demographics of your target audience. If it aims to target users coming from a developing world, do know that they have lower than average internet speeds, and the experience will be jarring to them.

3) Keep the video clip small. 10-15 seconds tops with looping. 

**Pro-tip** : Load a low res video, stretch it to fill complete screen and blur it using css. This has three advantages : you pack in less bytes, and the blur effect provides for a less distracting background, and there is no visible pixellation.

4) Make sure the there is enough contrast between text and background at all times.

**Pro-tip** Apply a overlay color to the video, and make the text white.

5) **DO NOT** use audio on the homepage. If there's anything more jarring than moving pictures without sound, its a video clip that stops every second to buffer. Very bad UX in my opinion.

6) Since the video serves as a background, avoid capturing too much detail, or framing lots of people and sudden movement. The more diffused it is, the better. It can still convey motion without seeming like you're trying too hard to get user's attention.

Take a look at few popular sites [that do it][1].


  [1]: http://www.creativebloq.com/web-design/video-backgrounds-2131982