Ever met with a client or talked to someone in your organisation and asked "what's our strategy"? If it's social media and they say "we have Facebook, do you think we need Instagram" you groan and think "they need to work some stuff out"? Welcome to strategy!
A Nine Step Social Media Strategy asks the questions that can be answered in a document with examples for staff and other stakeholders can implement.
Other documents such as Resourcing (staff/money) and Staff Guidelines (Thou Shalt/Nots) come from the strategy. But this will get you started.