The most effective direct marketing campaign you can conduct involves creating a series of personal letters addressed to your 100 best prospects. For a short campaign, write a six letters, each incorporating a progressively harder sell, and mail them two or three weeks apart. Create a newsletter to keep your name in front of your customers and prospects. Mail your newsletter monthly if possible, but at least quarterly. Offer a FREE instructional or informational booklet.
Booklets are easy and cheap to produce.
Using effective teaser copy on the envelope is your best bet.