Netiquette

A few words in an email can make or break relations...personal, professional and/or otherwise... It's strange to see people struggle with something as simple as writing a letter - striking a balance with the right mix of humor and seriousness.

This link is a good start
http://email.about.com/od/netiquettetips/

Here is a list of all that is covered in that page... the tiniest of things matter.