Here are some interesting examples of campaigns that have gone viral and marketing tactics that worked.
Create campaigns that do not use stereotypical images and context

Images of your product in a supermodel’s hand as she sits looking bored and passive are not going to work in a viral marketing context. To advertise their new LED TVs, Samsung strapped some LED lights onto sheep and ‘created’ works of art. The jump from LED TVs to LED sheep is a big one, you have to make that jump to get to the 19 million views of this video.

Bring your marketing into the real world

This is where my previous mention of “America’s Funniest Home Videos” becomes relevant. A large number of successful viral marketing campaigns involve real people reacting to imagined situations. Think about TNT’s ‘Drama Button’ campaign. It brought the drama of an intense show onto the streets of Belgium, shocking the real people on the streets. People loved it because they could see themselves in those reactions.

Take your products to extremes

Say you sell a boring product that has been seen countless times in homes and on TVs doing its job, like blenders. BlendTec was a company in this situation. Their Will it Blend campaign saw them use their blenders on nearly every Apple product, copies of the latest popular video game, paintballs, and DVDs of Justin Bieber. If you can’t see how that type of content can spread rapidly, you’re in the wrong business.

Reward your customers with your product

My favorite example of this right now is Pepsi’s #FutbolNow campaign. They have installed video games into the front of their machines. The game is a soccer challenge that tracks your real movements and judges how well you can juggle a soccer ball. You are rewarded with a free Pepsi if you reach a certain score. What’s the cost of a few cans of Pepsi next to drawing constant attention to your machine?

Team up with unlikely partners

Working with people outside of your usual industry can help you create a buzz for both of your companies. The TV show The Walking Dead teamed up with UC Irvine to create an open online course on what a zombie apocalypse would be like. Zombie lovers ate it up like free brains. Both the show and the university benefitted. HP teamed up with Kiva to allow HP employees an extra $25 to donate to the Kiva project of their choice. Both HP and Kiva gained exposure, while worthy charitable causes received funding.

Source: Jeff Bullas’ Blog