Remember, there is a real person on the other end. You are responsible for what you write. Keep your messages short to conserve bandwidth and save the resources of those subscribers who must pay to receive messages. Some gateways also limit the size of mail they accept. Use a descriptive subject line.
Many people decide whether they want to read a message based on the content of the subject line.
Sign all your messages. It helps to have at least a name to associate with a post and some mailers strip off the header, so the receiver cannot reply unless there is some kind of internal address. Be tolerant of newcomers. We were all new to this medium at one time, we are all still learning, and procedures are still being refined. Also, in the interest of clarity and ease of use in text retrieval programs, it's a good idea to use single columns of ingredients.