What do you really want to achieve? No sense in diving into an ocean willy-nilly; decide what you're doing it for: Visibility? Higher conversions over a period of time? Stronger brand resonance within a given group?
What are you willing to give to get it? How much time, and how many resources, can you devote to the effort?
Where is your audience? "Social media" covers a broad range of technology, including Facebook, Twitter and a wide range of community-building efforts.
How are you going to speak to them? Are you a Zappos-style brand, where the CEO is willing to take time and effort to serve on social media's front lines? Or maybe you're more Adobe-esque, with branches so diverse that it's best to serve multiple customers with multiple identities, depending on their needs.