Three fundamental questions to answer before a good idea can be a viral idea:
1.) Would anyone with no interest in this product care about the idea? It needs to hold a human truth that transcends what the agency or client thinks is good.
2.) Is it new? There must be a hook that makes you want to explore and share.
3.) Does it help express something on behalf of an audience in a way that they can’t? It should help them articulate love, loss, hope, fear, or hope, etc, to their friends and family.
Advertising Concept Book (Second Edition) by Pete Barry citing Ed Robinson of The Viral Factory