Get to the point.

1. Subjects with keywords.

ACTION – Compulsory for the recipient to take some action
SIGN – Requires the signature of the recipient
INFO – For informational purposes only, and there is no response or action required
DECISION – Requires a decision by the recipient
REQUEST – Seeks permission or approval by the recipient
COORD – Coordination by or with the recipient is needed

2. Bottom Line Up Front (BLUF)
3. Be economical.