Promise plenty and deliver even more. A common lament in marketing circles is to ;under,promise and over,deliver;. Giving the prospect more than they expect is a great way to delight customers and ensure they buy again. But ;under,promising; is self, defeating. The basis for all good sales copy is to deliver a big promise , a huge benefit that's sure to capture interest and resonate with your target audience. Make a huge promise and deliver even more.