Here are some mailing list guidelines that should be useful for starting a new group or neatening up an old one. These sample mailing list rules are based on typical rules that have worked for other groups. Most email discussion groups have found it useful to have some rules which all members abide by. Usually each rule is formulated to resolve a particular problem that came up. So you might want to borrow some of the wisdom of those that have come before you, and adopt some of these guidelines for your list.
General Mailing List Guidelines
Email Mechanics and Formatting Mailing List Guidelines (More on Formatting Plain Text Email)
And if there is another guideline that has been useful for your group, please let us know, in a comment below. Also, guidelines are a great way to foster a positive community culture.