There are many names for viral marketing. Buzz marketing or WOM – word-of-mouth marketing are other names. Its common metric is ‘pass-along’ rate. 

Viral marketing is about how other people tell other people about you or your creation. The fact is you don’t have any control over what goes viral. There can be negative viral marketing also. Once it goes, you can’t stop it – even if it is negative publicity.

There are just four factors for a message to go viral.

1. It must have a unique WOW factor. Wow does not mean just ‘that’s nice’, it means ‘Holy s$@# did you see this?’ OR/AND, it must be funny – so funny that you don’t just LOL, you LMFAF, OR/AND, it evokes emotion – makes you cry or inspires you or motivates you to do something.
2. Second, the message is NOT about you or your company. It is about your audience. As a matter of fact, you don’t create a viral message, your audience does. You don’t say ‘let’s create a viral message’. 
3. Finally, define a clear outcome. Going Viral is NOT the outcome. The message must clearly say or evoke the outcome from your audience. Also, ‘sales’ is not a desired outcome. Connecting, or building credibility can be a desired outcome that can lead to sales.
4. Finally, choosing an appropriate method or medium. This will depend on the goal and your audience. 

Therefore, going viral or creating viral messages is about engagement with your audience and building a trustworthy relationship.