#1. If you have a signature, STOP writing your name at the end of your email. Redundancy kills.
#2. If someone asks for help, via mass email, DON'T email your life story as to why you can't help. Seriously, just don't reply. Save time.
#3. DON'T write something vague in the subject line, then post a link to a cat video in your email. Knock it off.