We all use email for a living now. It's convenient. It creates a trail of history. It can even be oh so efficient because you can CC the world keeping everyone in the loop.
Just keep this in mind: Sometimes less is more. In business email, here are some rules I have developed over the many failed projects that crumbled, in part, due to botched electronic communication.
1. Don't CC someone unless they need to know. (and if you do need to let someone know and your email is monster long with old threads, tell them what part they need to read or send them a separate note with only the important stuff included)
2. NEVER BCC someone as a way of letting them in on a secret. They hit REPLY ALL and you're screwed.
3. Zero emotion unless it's a smiley face letting them know the closing is scheduled and will be problem-free. (even that's a risky one)
4. Keep sentences short. Read your note, then see how many words you can remove and still keep the same message.
5. Don't use LOL or LMAO abbreviations -- even if your 20-something buyer/seller does.
6. Include your contact info in every communication. Never make a customer search for how to call you.
7. Never SEND an email if you're angry. Writing it is fine, just don't send it until you've chilled. (also, if you do compose while you're agitated, DO NOT put the customer email address in there. USE YOUR address in the event of premature e-sendulation.
8. If you're sending important stuff and you're not a good writer, Have someone proof it. Presentation matters.
9. Don't spend time formatting the message. Use words to express what's needed, not 20 point red bold face fonts. If you need action, then end with ACTION NEEDED FROM YOU... (putting ACTION NEEDED in the subject is also a good idea)
10. Avoid slang especially when dealing with those who don't have English as their native language. If you need to drive home this point, go here and put in your favorite expression and see how it comes back. Now you know where "I think something got lost in the translation" originated.
"I think we are kicking a dead horse here" translates to "Task the fact that we give a horse that dies here to an effect."
...and of course the obvious. Writing an email in ALL UPPER CASE means you are either really upset or a techno idiot, both impressions are good to avoid. :)