It's more important to set guidelines for yourself than for members. You should be able to answer all of these questions:
How do you respond if someone threatens you?
What should you do if a member threatens another member?
What do you do if members discuss something illegal in the community?
How do you react if a member threatens to commit suicide?
Should you swear if your members do?
How do you handle criticism of your organization?
How do you handle personal criticism of you?
How do you handle bullying of members?
Are you happy for members to add you on Facebook?
Do you adopt a tone of voice to suit the community or use your own natural tone of voice?
What happens when you go on holiday?
What do you do if another individual or organization threatens to take you to court for something that happenened in your community? (surprisingly common)
Two more things here. First, you must consistently apply your guidelines in every circumstance. No exceptions. Second, you must decide how to respond to these situations before you launch the community.