Hi, Ray
I don't know if this would come under the category of "netiquette," but, as a corollary of your first suggestion, I'd say also read through your email before sending to be sure it's really saying what you want it to say. People can be trying to express themselves in words and think their typed words are saying what's in their heads, but it may actually 'say' something different as far as the recipient is concerned. See that your email is conveying the meaning that you're trying to get across.
Also, get a feel for the attitude that it conveys. You may be saying what you want to, but the way it's written may not be accurate. The recipient may take something as being blunt or rude when it was never intended that way.
This 'check' is esp. important to remember if you have a spell-checker in your email program. Some people will simply make sure there are no errors and send it away w/o considering how the email will 'come across' to their readers.