Seth Goden posted a great list of 36 things to check before you send that email. My favorites include:
13. Am I angry? (If so, save as draft and come back to the note in one hour).
26. Am I forwarding someone else’s mail? (If so, will they be happy when they find out?)
35. Bonus: Does the subject line make it easy to understand what’s to come and likely it will get filed properly?
36. If I had to pay 42 cents to send this email, would I?
Hat Tip: Roger Matus