Whether you are sending a marketing letter to your entire database or a single person, make sure your message has a point. What action do you want the reader to take? I've read plenty of marketing letters that expound for paragraphs about how great the company is and all they can do for me. But they never ask for the sale.

People sometimes get so wrapped up in the writing process that they forget that their primary purpose is to cause the reader to do something: call, click on the link, attend a seminar, etc.

Be specific. Tell your readers what you expect of them. Don't make them guess.

If you're not sure whether you're making your point well enough, hire a professional writer. You want to make a good impression each time your marketing materials reach your prospects. With opt-out functions, there might not be a next time.