These are recommendations rather than rules. In the tradition of the Internet, here I have appropriated, and altered other's hard work for this list. When sending messages to a discussion list, or posting on Caucus, keep the following suggestions in mind. They will help keep the group user-friendly for everyone. Keep each line in your message shorter than 70 characters.
Longer lines can cause problems with some e-mail systems.
When replying to another message, try to refrain from quoting entire messages. Paraphrasing or quoting selectively are both kinder to people's eyes and e-mail boxes. Long signatures are discouraged. They may be humorous the first time, but get old quickly. 2-4 lines should be sufficient to include any necessary information.