Garner interest, and identify your target audience
When you're writing a sales letter, it needs to be interesting enough to be read. One of the first questions you will need to answer is who your target audience is. Who are the individuals who are most interested in the product or service you're trying to sell?
Grab the audience's attention
As with any sales letter, you're going to want to grab the readers' attention right away. If you don't do that, you might as well be writing nutritional information on the side of a cereal box, because that's about how much what you are going to write will interest your readers. Jobs in sales require grabbing and retaining the target audience's attention during the sales letter, and afterward, interest them long enough to get them to consider the product or service.
Again, as with all jobs in sales, writing a good sales letter depends on first impressions. So just as you might work hard to make your first impression with a face-to-face (or phone) sale, so, too, do you have to work to make a good impression with your first sentence in your sales letter.
So make it something catchy, friendly, and professional all at the same time. Go ahead and flatter a little bit — but don't lay it on too thick. Today's consumers are savvy, and they're not going to buy a lot of ‘overt’ flattery; they'll simply know you're trying to sell them something. This can be a big turnoff.
So you could say something to the effect of, ''As an expert in your profession, you know how important X is. And of course, you also know that...'' Remember to ''Talk'' to your audience as though you’re talking to just one individual and not an entire audience.
Give good advice, and good information
You have to show your prospect that he or she has a situation you are familiar with, and that you know how to fix it. Illustrate (don’t tell) how your product or service is going to help your reader solve their problem. Try to convince your reader that your product or service is well worth the money the customer's about to pay for it.
After you have made it clear how much your product or service is going to be of benefit to your prospect, you can illustrate its advantages.
Be logical and to the point
"Walk" your customer through the advantages of the product, and why he or she needs it, one step at a time. Do this in a logical, subtle, and persuasive way. Don't use long, flowery phrases. Instead, short explanatory sentences are best -- and it's best if you keep the letter short, too. Numbered or bulleted points are not only fine, but are actually desirable if they are going to help the customer understand the benefits of your product or service.
Close with a call to action
At the very last paragraph, you have to close your sales "presentation" (in this case, the letter) with a call to action that's going to entice your prospect to act. You can also include a tear off a section at the very bottom of the letter so the prospect simply has to fill in his or her name and contact information if he or she would like more information, or to send in an order form. You can also tell the customer how he or she can order the product or service online.