This past weekend, I did a Wow-show. Among the questions I got was, “How can you use email effectively?”
My answer went on for awhile…. Below, the highlights, the gist, the top line message….:
1. Use Your Subject Line Wisely
Leaving aside the subject lines I never, ever want to see (“Crisis!” “URGENT”, “For when you get in on Monday” “I know you’re out sick but….”) It’s critical to choose your subject line with care. It needs to be pertinent, timely, and as compelling to the reader as it is to you.
2. Don’t Be Seduced by its Immediacy. (i.e. Don’t Get Careless/Crazy) 
In my experience, careless occurs when the communication is flowing along—zip, zip, zip—and the next thing you know you’re sending out emails that are not only grammatically incorrect or riddled with misspellings, but you’ve also found you’ve divulged far, far too much personal information, AND inadvertently hit “Reply All.” Crazy occurs when you send an email and get no response, at which point it’s possible you tell yourself that you KNOW he or she has read it; why haven’t you gotten a response? And then the internal storytelling begins—he must have thought this, she must have felt that….It simply wasn’t possible that he or she had stepped out to walk around the block, or get a coffee, or meet their mother. No. Their non-response was DIRECTLY attributable to your email.
Which generally leads to:
3. Do not use email for problem solving:
Frankly, you might as well get out gasoline and a match. In my experience, very VERY few people read a confrontational email and think, “Gosh, s/he is right and I am wrong! Let me write and say so.”

So, please, handle email with care.