The basic idea of any viral video is to attract, grasp and involve people so that people into the message they want to convey to the people out there.
Many crucial things are to be kept in mind while making such videos. You should keep it short: make your video 15–30 seconds. If it’s part of a larger story then break it into smaller clips. It would be rather better if you make it re-mixable – i.e. make a video that can be remixed by various people, many times.
And, please do not forget. I repeat. Don’t just make it an ad: make the video amazing, not an advertisement. That’s the real art if you make a promo not look like a traditional or a promo indeed, and then only are there chances of it going viral.
Amongst many upcoming viral videos making companies Showboat Entertainment just stands out of the bunch. They are in the industry for nearly ten years now. Showboat has made some excellent viral videos over the years.