By incorporating detail into your subject lines, you enable the recipient to more easily sort, categorize, prioritize and file your message. “Please bring the attached handout to the Tuesday, 2/10 staff meeting” is much more precise and efficient than “Staff Meeting.”
As an added benefit, when he or she responds, you will know exactly which memo is being responded to.
Sometimes, the entire brief message can be in the subject line. By placing “EOM” (abbreviation for End of Message) at the end of the subject line, the reader will know that there is no need to open the email.
Excerpted from Inbox Detox, Acanthus Publishing, 2009