Last year I wrote an article for www.smallbiztrends.com about how to write better business communications. By following 5 straightforward steps (notice I didn't say simple or easy) it's possible to begin improving your writing today.
http://smallbiztrends.com/2011/02/five-steps-better-business-writing.html
Visit this link for the full article.
This example uses many of the best practices expressed in the PowerPoint presentation above.
There are multiple sites dedicated to email etiquette. Here is a comprehensive PDF from one of them.
Formatting isn't everything. For more insight on how to write effective emails follow this link to my packet.
Block style is the most common for business letters. It's always wise to get an example of a letter from the specific company you're writing for to make sure you learn any specifics in the organization's style. Modified block style is another, less often used, style.
Source: http://businessletterformat.org/
Don't leave quality writing up to chance. Use this checklist to make sure you have written the strongest communication possible.