The sales letter format should emphasize key points while maintaining simplicity. Do not repel the customers or clients. Have normal spacing between lines and the contents just right so that the reader does not feel over_burdened reading your letter. Get the reader to feel as if he is invaluable to you and your company. The pronoun "you" in place of "we" instills a sense of warmth in the reader, drawing them closer to your business.
If you want results for your efforts, then what you really need is to understand the most critical aspects of the cover letter. The format is just one aspect. There are more details that you have to take into account. The content is the most essential point you have to bank upon. You might have a very crisp paper with nice format in it but it will not be helpful if you do not indicate the skills and credentials required for a certain job position. Of course, you need to possess the same essential skills, traits and knowledge. Thus, you must evaluate first your qualifications before aiming for the brightest cover letter format.