If you seriously want to gain higher response rates for your direct mail, then at some time you really should read the theory section. Theory is what most people avoid, but if you don't know why something works, it is hard to make predictions and to improve the number of replies you get.
But you might say, does it always work? Do you really know what you are talking about? Does every mailshot you create really work brilliantly? Read the answer by clicking "Success?"
If you want to stay in touch with what direct mail is all about day by day, go to the newsgroups. They are free, there is no advertising, and they tell you everything you need to know.
At this stage, if you have read other pieces about direct mail which tell you what to do without going into all this theory stuff, you might also be having some doubts. If you want to see why we disagree with these people who just set out lots of rules, take a look at the "rules" website but please don't forget to come back here, and then move on to The Theory.