Of those, only a fraction will respond. By increasing the size of your ad to that of a four column inch display ad you may attract many times more inquiries for a modest increase in cost. You'll see more on testing, later. Test just one element of your offer at a time. Sell benefits, not features.
Offers sell .
In your sales letter ask repeatedly for their order. And don't just mail once to a customer. Television advertisers say that it takes at least seventeen impressions before a genuine prospect responds to a commercial. In direct mail, experts say they can continue to mail to the exact same mailing list three to seven times before response drops too low to be profitable. Again, repetition is the key.