Purpose of the policy
Clearly define what the policy is for and who it is aimed at and include information about legal requirements. Be positive and encourage employees to use it. Make the policy available. Don’t bury it on a website that people only visit as part of their induction in the first six weeks of their employment. For a library why not place on the staff intranet? Warwick University library does not have a social media policy. The entire program has grown organically and not suffered as a result. So consider whether you need a policy?
Define social media
Many people will have very different ideas or no idea at all about what this constitutes so best to make it as clear as possible from the start. It might be of some benefit to detail what social media is not, as well. Create the policy as a wiki and you can keep it up-to-date as technology changes.
This is the key to social media from a library perspective so perhaps consider what tools can be used to communicate specific messages effectively. Don’t simply re-broadcast information that appears on a website and don’t link your Facebook page to your Twitter account. Twitter is much better at linking and pointing to other resources and for opening conversations, posing questions. So look to empower patrons to become involved: run competitions, build relations and hence a community of followers.
Weighty policy documents can be a complete turn-off to people and can extinguish any interest in the subject. Keep it short and sweet and be inclusive in its circulation and promotion. A searchable pdf document is far more accessible than a static page on a website.
Ensure users comment as themselves, identify who they are, who they work for and what they do there. Don’t pretend to be someone else (bad etiquette) as this can reflect badly on an institution. Also think before you post as it is difficult to take something back written in the heat of the moment. Review what you have written before you post.