If you write long messages that drift from one subject to the next, your reader's attention will drift as well. Also, take the time to delete long header text when you're forwarding or replying to an e-mail. This shows the recipient that you know their time is valuable, too. And above all, proofread your message for spelling and grammar before you send it. In cyberspace, people only know you from what you type. If you're sloppy with the basics, how can anyone trust you when it's really important?
Always fill-in the subject line! When you start receiving dozens of e-mails a day, you'll come to appreciate people who use subject lines. The subject line is the only label you have to identify each of the messages in your mailbox. Use something appropriate, such as the topic sentence or the main idea. Be sure to keep it brief, though, since most e-mail clients only show the first 20-30 characters of the subject line anyway.
Be careful with formatting. Remember that not everyone uses the same software to read their e-mail. Just because you can center your text and make it green and boldface doesn't mean your recipient can too!
