Following his advice, my company generated millions of dollars in five years, just from offering new products and services to existing mailing list customers, items that were related to what they'd bought before. It was so simple! He wrote the sales copy, we had it typed and sent out, and we raked in the money. Spend more time with your existing customers. That is the most powerful thing you can do with direct mail.
Your house mailing list is everything. You've got to keep testing and trying different things with them, and direct mail is the ultimate way to do that. None of your direct mail strategies are worth anything if you're mailing your offers to the mailing list wrong lists -- no matter how perfect everything may be. Back when I started my business in 1988, we were using space advertisements in national magazines to generate leads -- and were astounded by the amount of money we were making.
Then we met our mentor, the man who introduced us to direct mail... and within a few months, we were making literally 25 times more money than space advertising earned us. Now we mail out millions of pieces of mail every year, because mailing list direct mail marketing is still the easiest way to make money that we know of. It's an exciting medium.