Ask yourself these questions:
What are they sharing? Why are they sharing it?
When you think about it, people have been sharing thoughts about products, services and information for years. Before the internet there were TV ads, and magazine ads, and newspaper ads. Plus, there were discussions around cocktails, at work, "around the water cooler", at the gym, as well as other places and events.
People have been sharing content forever, even when it was on a stone tablet. The difference today is that the sharing of content is lightning fast. We literally just click a button and voilà - it's shared. Very little thought has to go behind that type of sharing.
There are many reasons people share content online and offline.
They share it to be helpful, to entertain, to do something fulfilling. People share things simply to market their products, services and ideas to others. They also share big ideas in order to differentiate themselves from others.
As a small to medium sized business owner, if you can focus on sharing to bring value to your audience via the content you choose or create, then you will do very well. But, the content needs to be something your audience will share for another reason. They don't care if they promote you; they only care if the idea they're sharing is important, affects someone else, or themselves.
Research and get to know your audience and the competition.
It's important to know your audience to understand what will entice them to share. Your audience may have a variety of triggers that make them want to share, and some that make them not want to share. It's important that you learn about these triggers so that you can leverage them in your online marketing campaigns.
Studying your competition, and their audience, to see what is shared can help you work out what you should be doing with your audience. You can use social media tools to search for terms to follow. Use individual tools for specific social media, like BrandTweet Statistics. http://stats.brandtweet.com/
Once you've conducted some research, take a look at your findings and create something you believe will be shared. Perhaps through your research you realized your audience likes short, to the point, and humorous memes. Can you add a graphic to your content that can also be used as a meme that is easily shared on Pinterest, Facebook and other social media networks? People may share the meme, but then be able to find the content due to your watermark on the meme or your link back to your content.