You could just send out your brochure to potential customers but it's much better to personalise your mailing with a well written sales letter.
Personalise - Using person's name in a sales letter will give you greatest success. It's feasible to address sales letters to - "Dear Transport Manager" or "Dear Friend" or "Dear Sir or Madam" or no salutation at all. However this lessens your chances of getting a response.
You must have a good headline - You've got to grab reader's attention as quickly as possible. There must be a reason for them to read on. The same rules apply that you'd use in your advertising or your brochure; you need to start with words such as - "How to" or "Discover" or "The Secrets of"
Start with an anecdote - Introduce your message with a short relevant story. For example, you might use something like this if you were introducing a management training program - "Seventy percent of employees don't leave their job they leave their manager" You'd then provide supportive statistics and give details on cost of staff turnover. You would then go on to show how you could reduce these costs and improve productivity through your training program
Lots of "You" and no "I" or "We" - Make each letter sound like you're speaking to that individual rather than to a group of people
It needs to tell reader what's in it for them - Tell them how they will personally benefit, how their business will benefit and/or how their problem will be resolved
Be believable - Don't make "fantastic" claims for your product or service - your letter has to be credible
Write letter as if you were speaking to person - It has to sound human - warm, friendly, sincere; not too businesslike. Read your letter out loud and if it sounds pompous or businesslike - re-write it