The Heart of Direct Mail's Success
Approach tests include the testing of offer and copy. They are aimed at gaining a direct increase in response. Approach tests are the tests your prospects and customers see.
While many, many direct mail test rules still apply today, please understand that times are changing. To succeed, you need to do more tests - and that means failing more often. However, remember that failure is only bad when you don't learn from it, so don't be shy about testing out-of-the-box ideas here and there to see what they may do for results. Safe tests usually yield little lifts; radical tests often can lead to huge gains. Due to information overload today, I have seen many "unthinkable" tests work amazingly well recently.
If you are told self-mailers never work for your industry, test self-mailers. Test different lists that seem odd but match your current customer profile. I have had success with a humane society by mailing Victoria's Secret catalog buyers, for instance. Test lists, then offers/messaging, before new creative.
You also should pay close attention to your marketing segments. For example, what works for baby boomers is different than what works for Gen X-ers, and both definitely are different than Gen Y-ers.
Keep in mind that you test to gain insight and information that can be applied to future efforts. While that may seem obvious, I still see a lot of premature creative tests done long before lists and offer/messaging options are exhausted.