Marketing letters and emails allow you to reach out to potential customers individually, instead of relying on television commercials or print ads to get their attention. You can use this personal connection to set yourself apart from your competition, even if you have a small budget or lack a marketing team. Effective marketing letters or emails address the needs of a specific audience and describe precisely how they'll benefit from giving you their business.

Format Correctly

Keep your letter simple, avoiding too many graphics or colors. A cluttered letter is difficult to read and looks more like junk mail than business correspondence. Cluttered emails with moving graphics and pop-ups are even worse. Pretend you're speaking to the person one-on-one, using a conversational tone and avoiding jargon. Use a formal salutation such as "Dear Mr. Jacobs." Addressing the prospect by his first name is inappropriate unless you know him personally, and using his last name signifies respect.

Define Your Target Audience

You're more likely to connect with potential clients if you write your marketing letter or email with their needs and values in mind. Narrow your target demographic as much as possible, considering characteristics like age, gender and income. Write from the customer's point of view, thinking about what you'd relate to if you were an upper-middle class woman in her 30s with a new baby, for example, or a man in his 50s planning for retirement.

Grab The Reader's Attention

Don't count on prospects reading all the way through to the end before they can see what you have to offer. Instead, begin with an opening so intriguing they can't help but read on. Demonstrate that you understand them by describing a challenge they face or by finding common ground. In the "Forbes" article "The Ridiculously Inexpensive Magic of Direct Mail Letters," marketing consultant Lois Geller says one of her favorite opening lines is "I don't know how you feel about (whatever), but I know I ..."

Focus on the Reader

Instead of just describing your product or service, elaborate on how readers will benefit from using it. When prospects read your letter, their first question is "What's in it for me?" Address this by describing specific benefits, for example that your coaching services can help them boost their sales by 10 percent. In the "Entrepreneur" article "Write a Great Sales Letter," marketing expert Kim T. Gordon says a good sales letter always includes in the first paragraph how the client will benefit from hiring you.

Make an Offer

Show customers it's worth their time to learn more about your company. Offer a deep discount, free or trial service or other offer that's valuable to the consumer but doesn't require a significant time or financial investment on your part. No matter how attractive you make your product or service seem in your letter, prospects need an incentive to invest their energy in your company. Create an offer they can only get by responding to your letter. When they take you up on your offer, they might also purchase additional services from you. For example, if you offer new customers a half-price membership at your gym, they might also sign up for sessions with a physical trainer.

Ask for the Sale

Close your letter with a call to action, in which you tell readers what you want them to do next. It's not enough to sell prospective customers on the benefits of your products or services, you must also tell them exactly how to hire you, purchase your products or learn more. Tell readers to visit your website, call to set up an appointment or come to your location to browse your products, and include all of your contact information. Emails are particularly suited to this technique, since with a carefully-placed embedded link, customers can go directly to your website or product page - they don't even have to pick up the phone!