The rules of retailing on social media are finite, says Crystal Vilkaitis, owner and CEO of Crystal Media, which advises companies (including jewelry brands) on social selling. When marketers follow them—and use the right tools—“they see great results.” But the rules on the most ­retail-friendly platforms—notably Facebook, Instagram, and Pinterest—change frequently, as developers tinker with tools and refine algorithms. For time-pressed retailers, this can make the prospect of social selling particularly daunting. We asked Vilkaitis to break down the basics of making your social feeds shoppable. The best part? The setup is all free. Facebook Facebook may not be the slickest platform, but it’s still the ­biggest. According to a 2016 poll by the Pew Research Center, more than 75 percent of adult Internet users use it. Selling products on Facebook means advertisi