There are the general guidelines which I follow while emailing:
:: Write clearly and concisely. Avoid ambiguity, make single points simply, avoid subtlety, avoid sarcasm, and keep sentences short.
:: Read first, send later. If you are angry, annoyed, frustrated, or emotional, hold back until you have taken a breath and read your composition from the perspective of the recipient.
:: Watch your grammar. A misplaced sentence can give a whole other meaning to what you have written, literally.
:: Buy time. If you can’t respond quickly, for whatever reason, send a quick ‘holding’ e-mail to tell the sender that you received their communication, are aware of its requirements, and will get to it. It’s often a good idea to give an approximate time-frame for your response.
:: E-mail is a conversation. Greet and meet the recipient; sign off cordially; be concerned with being interested more than being interesting; don’t monologue – invite an exchange rather than deliver a speech.
:: Use technology to your advantage. Set up work flows and configure your mail application to assist you in managing e-mail exchanges with the minimum of fuss to you, and the maximum of benefit to all parties.
Would you like to add up your advice?