I love this post: Hacking Email: 99 Email Security and Productivity Tips, especially the section on email etiquette.  Many of the tips provided by the IT Security Staff point to one common theme: DON’T WASTE PEOPLE’S TIME with your email.  The objective is to get your message read, not to slow down your reader.  Sending an email with a blank subject or a subject like "Hi" is sure to get it deleted.  Be detailed in the subject line, so they don’t have to read three paragraphs to understand what you want.  Don’t send chain letters.  Don’t forward your motivational saying of the day.  Don’t "Reply to All" on a CC with 43 people.  Take the time to cut the most relevant sentence from the message to which you are responding and answer specifically, so the reader doesn’t have to review the entire string to figure out what part you’re answering.  Be brief; if not, provide a summary before the text.  Bottom line: use common sense and courtesy.  Don’t cut corners to save yourself time and put the burden on the recipient.  Ask yourself, "What could I do to save my reader some time?" before sending.