Social media is quickly becoming one of the best ways to get your message out to your customers. To do that however, you need people following you. WordPress has several tools built in that could assist you in this area.
Social Marketing Plugin
One option that you have available is the use of the Social Marketing plugin. This plugin allows you to give away coupons, discount codes or even downloads once someone completes a simple social task such as liking your facebook page or mentioning you on twitter.
More information on this plugin can be found on the wpmudev's Social Marketing page. Just click the usage tab.
Social Toolbar Pro Plugin
Social Toolbar Pro ads a toolbar to the bottom of your site for social media. There users can receive your latest tweets, find links to your social sites and even "like" your page.
You visit the Social Toolbar Pro website for more information about the plugin and how to use it.