Learn to Write Well
A great book on writing for business is "Writing for Design Professionals: A Guide to Writing Successful Proposals, Letters, Brochures, Portfolios, Reports, Presentations, and Job Applications," by Stephen A Kliment.
A few helpful writing tips.
+ Be concise and to the point
+ Write the way you would speak
+ Use grammar/punctuate correctly
+ Spell correctly
+ Keep sentences short
+ Make sense in your writings
+ Keeps things simple
+ Don't use technical babble, it will confuse