I’ve found the most common mistake businesses make on social media is pushing their product or service in spammy way. Most people on social networks are interested in connecting, interacting, and building relationships.  Not being sold to.  
Which means engagement strategy is a biggy and should be given some thought.
So be sure to engage your customers, ask them questions, do polls or contests.  Give your opinion on industry trends, tell stories about your business.  Let people get to know you.  Customers interested in buying from faceless brands are a thing of the past.

Will all of this pay off?  Not immediately.  Stick with it long enough so that people see you’re serious, and it certainly will.  You’ll get more Facebook fans, links, online comments, and bookmarks; everything you could ask for to increase exposure and business.
And they won’t do this because you offered a gift certificate or some other incentive.  They’ll do it because they know you, like you, and trust you. 
Truth is you can’t buy that kind of marketing.