Don’t send an attachment when you could put the text in the body of the message. Not everyone can open your attachment and in these days of viruses, many are afraid to open attachments.
DO NOT USE ALL CAPITALS.
On the Internet, this is the equivalent of screaming at someone.
Do not spam your peers.
Use fonts that are easy to read. While Curlz MT may be an interesting looking font, it is very difficult to read if used for more than a few words of text. On the same note, colors may be difficult for people to read. It is best to use colors in your text for emphasis only.