1. Send your sales letter to the right people.
  2. Personalize your sales letter.
  3. Write different versions of your sales letter for different segments of your target market.
  4. Include an order form with your sales letter.
  5. Don’t include fancy graphics in your sales letter.
  6. Don’t use mailing labels on your envelopes.
  7. Don’t put teaser copy on your envelopes.
  8. Send out a repeat mailing two or three weeks later.
  9. Put your sales letter on the Web.
  10. Be realistic about the response rates your sales letter may generate.

Source: Susan Ward