What to Do
Do Use a Spell Checker
Okay, we know this sounds simple, but it's important. And even though it's important, many netters decide that their time is too precious to waste checking over the e-mail for typos. Not only does this look unprofessional, it can seriously damage the intent of the message. Imagine sending the following careless e-mail to your boss:
You're dog is sick.... wife says to bring home medecine.
Not only do you risk insulting your boss by appearing to call him or her, or his wife, a dog ("you're" means "you are"), you also abuse the person's intelligence with poor grammar and misspellings. A clean, typo-free letter bespeaks volumes of your abilities, regardless of your career path (even if your job has nothing to do with grammar). Whether it's to the CEO of your ideal company or your crazy cousin, perform the spell checker on your letter, and re-read it for clarity. Both you and the recipient of the e-mail will be forever grateful. Even if they never know it.
Do Use Proper Capitalization
Again, this sounds like a no-brainer, but so many people continue to write in ALL CAPS, or the reverse, no caps. Writing in capital letters is the equivalent of screaming in someone's ear. If you consider that polite behavior, continue the assault. Just remember that most people don't enjoy being yelled at. Similarly, some people have the tendency to avoid capital letters altogether. This is the equivalent of whispering. If your message is important, go ahead and say it -- in normal volume, with regular capitalization. If you write your I's in lower case, people looking for symbolism may assume that you don't have very much respect for yourself.