1. Refrain from partially starting a sentence in the subject line or typing a very long sentence in the subject line. It becomes hard for people to sort their e-mail and find what they are looking for when they want to refer back to a specific e-mail at a later time.

2. Never send an e-mail message without a subject. There are a couple problems with this. It becomes hard for people to sort their e-mail and find what they are looking for when they want to refer back to a specific e-mail later. Also many ISP's and anti-spam programs will consider this SPAM and block the message from reaching the recipient.
 
3. Don't Cc a large group of friends who don't know each other when sending out group messages. You should Bcc everyone for privacy reasons and to prevent the accidental "Reply To All" syndrome, which can be embarrassing when one of your recipient's comments on the subject matter of the e-mail and it goes out to all your friends and family. When you use Bcc the recipients can't see each other's e-mail addresses and therefore will only reply to you or the original sender, which keeps the responses private. (Cc is an acronym for Carbon copy and Bcc is an acronym for Blind carbon copy.)

4. Keep e-mails somewhat short, most people are way too busy these days to read pages and pages of e-mails.

5. If you are upset or angry about something and are sending an e-mail out you just wrote you may want to save it in your drafts and look at it later after you cool off. You will find that most of the time you will probably rewrite themessage. Remember once you click send there is no recalling the message back. It's probably easier to offend someone in avertedly in e-mail verses over the phone or face to face.
 
6. Please also understand when a recipient reads your e-mail depending on the mood he or she is on can dramatically affect the tone of the e-mail they are reading.

7. Be self conscious about what you write about in an e-mail, remember e-mails have a way of finding themselves in other people's hands (Look at the beloved Martha Stewart) and it's too easy for someone to forward a message, even if it's someone you think you trust.
 
8. Many E-mail programs cache or remember e-mail addresses you type allowing your e-mail program to auto complete the e-mail address of your recipient, take a quick look and confirm it's the right person you wish this particular e-mail message is intended for.

9. Please refrain from forwarding hoax e-mails without confirming their accuracy. I have seen many people over the years fall victim of fear and mean well when forwarding these types of e-mails to all their friends and families. Examples would include Bill Gates giving away free money, crazy viruses that will delete your C drive, People with foreign bank accounts with millions of dollars who need help getting the money transferred out a 3rd world country, etc.

10. Run spell check before sending your e-mail messages to correct common typos or misspellings.

11. Refrain from sending large attachments, most ISPs prohibit people from sending attachments over 5 Megabytes in size (Slightly larger than the size of a single MP3 file). If you are e-mailing pictures you may want to consider setting up an online photo album.
 
These free services allow you to upload tons of pictures for your friends and family to view and even order prints. When people order prints this is how the web site generates revenue.

12. If you are using your e-mail for business consider setting up a signature file with all your contact information. This is great way for your customers to find your phone number if they didn't put it in their address book yet.