A well-crafted cover letter is a key component of most successful business-to-business campaigns. Besides giving the impression of "one-to-one" communication, the narrative tone afforded by a letter makes it easier to deliver your message in a way that's compelling to the recipient.

We routinely get asked by clients to shorten letters as much as possible. The assumption is that most managers, etc. don't have the time to read a long letter.

Truth is, a successful cover letter can be virtually any length. Pick up a book on direct marketing, and you'll find examples of successful campaigns that featured letters as long as 10 pages! If you're asking the reader to buy product (in an upgrade campaign for example), then your letter will naturally be longer, because you need to deliver all the information that person needs to make the purchase decision.

More important than length is to first make your letter enticing, concise, compelling, easy to read, and above all, spur the reader to action. Here are a few guidelines to keep in mind:

1. Keep your paragraphs as short as possible.

Your recipient will decide in a few short seconds whether he or she wants to spend the time reading the entire letter. Short paragraphs (1-2 sentences only) make the letter look less intimidating, and also make it easier to read. If you have to compress two or three paragraphs into one in order to fit the letter onto one page, don't bother -- leave it "as is".

2. Use bullets and underlining to highlight key points.

Bullets and underlining both serve to break up the letter in the way described in #1 above. Underlining also highlights your most compelling messages such that if the reader first scans the letter, he or she will be more likely to proceed further. (Side note: don't use bold type if you can avoid it. It makes the letter look more "word-processed" and less personal.)

3. Keep it moving.

The reason a lot of successful copywriters use conjunctions (and, but) at the beginning of sentences and ellipses (...) at the end is to keep the reader moving. Don't allow your letter to bog down in information that's not critical to your message. A two-, three- or four-page letter can be highly successful if it's written in a way that's keeps the reader's interest.