Begin with a greeting (e.g., “Dear Mr. Smith”) rather than just launching into your question in the first line.
End with a closing salutation (e.g., “Sincerely,” “Best,” etc.) and your name, even if the person knows who you are.
Use proper grammar and spelling so that you are presenting yourself in the best possible light.
Use formal language rather than slang or more causal wording (e.g., “children” instead of “kids”).
Do not type in all capital letters. IT IS THE ONLINE EQUIVALENT OF YELLING.
Do not forward an e-mail unless you know that the person who sent it would not mind if others see it. Conversations are assumed to be private unless otherwise noted.
Keep the message history in the e-mail (i.e., don’t delete it). If you are having an extended conversation with someone, it can help to reference what has been said.
If you have a new topic for the same person, begin a new e-mail with an appropriate subject line.