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A sales letter is a piece of direct mail which is designed to persuade the reader to purchase a particular product or service in the absence of a salesman. It has been defined as "A form of direct mail in which an advertiser sends a letter to a potential customer."^[1] It is distinct from other direct mail techniques, such as the distribution of leaflets and catalogues, as the sales letter typically sells a single product or product line, and further tends to be mainly textual as opposed to graphics-based. It is typically used for products or services which, due to their price, are a considered purchase at medium or high value (typically tens to thousands of dollars). A sales letter is often, but not exclusively, the last stage of the sales process before the customer places an order, and is designed to ensure that the prospect is committed to becoming a customer.

Since the advent of the internet, the sales letter has become an integral part of internet marketing, and typically takes the form of an email or webpage. Unsolicited sales emails are known as spam, although spam typically consists of emails which are much shorter than a normal sales letter. Offline, unsolicited sales letters are known as junk mail.

Components[link]

An efficient sales letter contain four interrelated parts.

1-Getting the reader's attention.
2-Create interest and build desire for the product.
3-Offers convincing prooves.
4-Persuade the reader to act.

Formula[link]

As there are some set of rules for doing a particular thing.The formula for sales letter is known as "AIDA" formula. The AIDA formula is one of the important things you need to know for writing an effective, It is also known as sales-making technique. Wanna know more about it?

OK, now what does AIDA stands for? Here is the answer:

A is for attention,
I is for interest, 
D is for desire, 
and A is for action. 

Each initial plays an important role and is a must, in a good copy.

Let us jump into details –

Attention[link]

comes first. Users want quick and easy things. You have to grab prospects attention and it should be impressive enough to attract them to read further.

Headline is the very first thing to be noticed in your copy. Your headline can make the real difference. So make it strong.

                                   (tehzib husssain gcms mansehra)

Interest[link]

is the next important factor. Once you have acquired reader’s attention, you should know to hold their interest.

Provide some relevant facts; let them know how you can help, offer a solution to their problem.

Desire[link]

is an important issue. Talk about benefits, give real examples. As you probably have heard, benefits sell and not features.

Make them aware about how your suggested solution can make their life easy.

Action[link]

is the last but the most important phase of this process. Now you should do something that one should literally say yes I want this product, or I want to get updated information regarding the same.

This is where a passing by reads can turn into actual buyers. We can even say it. Whether you are selling a product or building a list, if your prospects wish to take desired action it is call to action (form your side).

Some relevant components[link]

The sales letter is split into several key sections. In addition, other sections may be used, such as sub-headlines.

Headline[link]

The headline is the most prominent text on the sales letter, and is designed to be among the first item the reader attends to understand.

Body copy[link]

This section is typically quite long, with 4, 8 and 16 page letters being common formats. This section will typically contain testimonials from the firm's customers as well as pictures and information about the product. On the internet, the body copy may include embedded video or audio.

Call to action[link]

All sales letters include a call to action which is intended to get the customer to commit to purchasing the product or service, typically without any further intervention.

Graphic design[link]

The graphic design of a sales letter is an important part of the branding. The font, layout, line spacing, paragraph formatting, images, etc. all have an effect on the efficacy of the letter.

Development of sales letters[link]

Because of the direct response nature of sales letters, they can be carefully tested on an ongoing basis to determine which version performs best in terms of converting readers to customers. Sales letters are typically developed incrementally, with split testing of various elements. This allows the marketeer or copywriter to confirm which headline, body text or graphic design converts best. On the internet, it is possible to track additional variables, such as the open rate of emails, the bounce rate, clickthrough to the checkout, etc.

Classic letters[link]

Some sales letters have become design classics in their own right, notably the letter by John Caples which sold a home study (also known as distance learning or correspondence course) in piano playing. This letter had the headline "They Laughed When I Sat Down At the Piano But When I Started to Play! --"^[2]

References[link]