OK, pay attention: here’s the theory bit. This is a diagram I sometimes use in lectures, to illustrate the shift from traditional to social media marketing.
So. The traditional, bog-standard marketing theory. Marketers have always tried to get us to trust them by passing their message down to us through traditional media channels. For big businesses that often means bombarding us with repeated TV ads. If they can get endorsements from experts, so much the better. But the people we trust most are our friends and family. The Holy Grail of marketing is ‘word of mouth’. People start talking about your product or service, recommending it to friends. It’s the most effective, yet the hardest thing to do with traditional media.
Traditional marketing theory describes this as a circle of influence - the layers of influence that marketers try to penetrate. It looks something like this:

But traditional marketing is less effective than it used to be. People tune out of TV and magazine ads, and spend more time online. Today, people listen to recommendations from peers rather than marketing from companies. Social media marketing might be represented as a merger of influence, like this:

It’s what happens when people become media and they market stuff for you and to each other. They create their own media (blogs, social networking profiles), they review and recommend, they pass on YouTube clips, they tag interesting media and websites with keywords so others can find them. It all gets mixed up.
Whenever someone becomes a fan of a Facebook page or a member of a Facebook group, that shows up in their news feed for all their friends to see. If it looks interesting to them, they’ll click on it.
And who are you going to trust? Trust today is in ‘people like me’ rather than in corporations. And that’s good news for small businesses, who can connect authentically with their customers and clients. Social media is a personal medium, and a small business owner can use it more credibly than a faceless corporation by expressing something of his or her personality.
People might have tenuous connections with distant nodes in their online social network; but they will still be more likely to listen to their recommendations - or even simply pay attention to what they’re doing and which products they’re consuming.
It’s not hard to tap into, and it’s not expensive. As a business, the first step is simply to make your stuff findable, so people can locate and recommend it. A website is essential. A blog is easy to start. A Facebook Group takes a few minutes to set up. If you’re feeling more adventurous, you might want to create some media that people can pass on and that you can track - such as a YouTube clip or a podcast.
Search is still the dominant form of advertising on the Internet. If you use social media, more people can find you in more ways. Yes, use Google AdWords (or other pay per click services) to help people find your website. A blog increases your natural search results. And it’s not all about Google. A podcast can be found by searching iTunes, a video by searching YouTube, a Facebook group by searching Facebook, a blog by searching Technorati, and just about anything can be tagged and saved in social bookmarking sites such as del.icio.us. And people are searching for the things they’re interested in all over the world, all the time.
Social media marketing is what we used to call word of mouth marketing. It’s just become much more powerful.