Viral marketing is all about encouraging people to spread information on a product by voluntarily sharing that information with people they know.

In the old days this would have been called 'word of mouth', and would have been a useful if undramatic complement to regular marketing. If you can get kids talking about your fizzy drink in the playground, lots will go and buy it.

Viral marketing on social media

What makes viral marketing such an exciting modern marketing phenomenon is that the 'people we know' no longer just means our immediate social circle, but everybody in our social media universe, and then multiples of people in multiple universes beyond that.

A viral campaign, if it comes off, can achieve dramatic results in days, even in hours, thanks to the exponential growth potential offered by exposure on the likes of Twitter, Facebook and YouTube.

Learning from the big business successes

The most successful viral campaign ever was for men's aftershave Old Spice, which until two years ago was the very embodiment of a moribund and unhip brand.

Its manufacturer Procter & Gamble asked ad agency Weiden+Kennedy to give the brand new life. The results changed the rules of social network marketing.

The campaign began with a televised ad shown during the 2010 Super Bowl, introducing a 'brand character' called Old Spice Man played by former American footballer Isaiah Mustafa. With a humorous twinkle in his eye, Old Spice Man promised women he was 'the man your man could smell like'.

The simple but crucial next step was to put the ad up on YouTube where its cheesy but accessible humour attracted over 13 million views in a matter of days. To date it has been seen over 40 million times and has spawned hundreds of copy-cat videos that have extended the viral effect even further.

Weiden+Kennedy bided its time for a few weeks and then posted a message on Old Spice's Facebook page, and on Twitter, inviting people to fire questions at Old Spice Man. A team stood by to post back near immediate video responses, all in keeping with the original character and its by now trademark tongue in cheek 'manliness'.

Over 180 of these videos were knocked out in a two day blitz, as a furore of enthusiastic participants jockeyed to get their question answered by the character, and then chat with each other online about the results.

A host of celebrities got sucked up in the frenzy, feeding the fire by involving their own legions of social media friends and followers. This was no accident. Celebrities known for their huge social media following were specifically targeted.

What are the lessons for small business?

At first sight, this does not seem like a trick that could be repeated by just any business and brand. Not everybody has the marketing power of P&G, and that kind of lightening doesn't strike every day in any case, does it?

But if one drills down into the essentials of the campaign, there are important elements that could be used by any small business wanting to get its brand in front of tens of thousands of potential buyers.

The most important lesson of the Old Spice campaign is that basic viral marketing does not have to cost a lot of money because you are harnessing people power to voluntarily promote your brand.

Building the idea for the viral

You need to start by coming up with a personality or persona that in some way represents your brand positioning. This could be a real person on video, or perhaps some kind of animation. The main thing is that it needs to be a character that people – the kind of people who buy your products - warm to and want to interact with. Is there a big personality on your staff? Or a local stand up comedian who could do with a few extra bob?