This is a great article by Dave Kerpen about simple ways to improve your writing:
Want To Be Taken Seriously? Become a Better Writer.
“The number of poorly written emails, resumes and blog posts I come across each month is both staggering and saddening. Their grammar is awful. There are dozens of misspellings. Language is much wordier or more complex than necessary. Some things I read literally make no sense at all to me.”