According to this MSN article:
"No matter what field you’re in or position you hold, the ability to communicate clearly, concisely and credibly in writing is a required and important skill for advancement in any organization."
1. Take a break before trying to proofread. Give your tired eyes and brain a rest.
2. Find a proofreading buddy, and check each other’s work. It’s easier to proof other people's writing than to do your own.
3. Proofread on paper (not on the screen)....easier on the eyes.
4. Proof text backward. That stops the tendency to skip words as you read and miss some of the errors.
5. Look things up when you're not 100 percent certain (e.g., fewer or less, comma or colon). Don't guess."
Another thing that works: paste your e-mail into Powerpoint. If your main issue/ask does not fit on one slide that is readable in hard-copy that you put at your feet (from 5-6 feet in other words) - go back boil it down. Refine it until it is easily readable and clearly understandable printed on one slide, from 5-6 feet away. Sorta like writing the newspaper headline to the content. Put extra detail in links that the reader can follow if they want to drill down.
The most important commodity a writer deals in is:
Don't waste it :-)