I found a nice tip sheet on writing efficient emails on the mighty Lifehacker website just now. You can read the article here. The main tip, pointed out in the Lifehacker entry, is to always revise. I try to remember to do that myself as much as possible. My favorite trick for proof reading is read what I wrote backwards. Start with the last sentence and move up the document. When you take what you wrote out of context it's easier to find errors. When you read a document from start to finish your brain edits and puts in words that aren't there because you expect them to be there.