According to Contagious: Why Things Catch On ideas and products that stick tend to be simple, unexpected and credible, with concrete details, an emotional undertow and a memorable story line.
Jonah Berger gives us 6 six principles that help make things go viral:
- Social currency (making people feel that they are cool insiders);
- Triggers (everyday reminders of an item or idea);
- Emotional resonance (making people want to share the experience with friends);
- Observability (that is, a highly visible item advertises itself);
- Usefulness (people like to share practical or helpful information);
- Storytelling (embedding a product or an idea in a narrative enhances its power).
Here is a critique by the New York times on this book
http://www.nytimes.com/2013/02/26/books/contagious-why-things-catch-on-by-jonah-berger.html