As you build your social media following on Facebook, twitter, Google+, LinkedIn, Pinterest, and others, you build up a large following of people that have the ability to share your content.
Every piece of content that hits your website should immediately be shared on your social media profiles. This can result in your social connections sharing the content also, generating 100% natural links, something that Google loves!
Also make sure that your website content is easily shareable by your visitors. It seems like an obvious tip, but you would be surprised at how many sites exist out there that do not have social sharing buttons. There are many options to match the look and feel of virtually every website out there.