NO chain letters or political endorsements. Keep It Short and Simple. Trim quoted material, and keep your signatures short. Messages carrying more than one prior message will probably be rejected. Summarize your post in the subject.
Descriptive subjects get more attention.
Post prudently, and send private emails when appropriate. These are blocked by the server. HTML or other formatting works very unreliably and sometimes will not come through at all. All the moderators will see your note. These serve no purpose and tend to offend many list-members.