in direct mail marketing. The difference is that when you try again in direct mail, you must change something.   How many times have you heard this quote, "If you keep doing what youve always done, youll keep getting what you always got." Testing is all about making small changes in order to achieve a higher response rate.   Once you get a respectable response from a direct mail piece it becomes your "control piece." You should always make small changes in your control piece and test them for a higher response. A respectable test mailing should be at least 1,000 pieces. This will give you an idea but to do a reliable test you should consider doing a 5,000 piece mail out.   Two of the biggest questions I receive in regards to testing are (1) How do I know what I should I change, and (2) Whats the best way to track my response rate?   To answer the first question, the following are the elements of the mail that I would tweak in order of importance:   1. List - Make sure youre sending to the right group of people! 2. Envelope - You must get your piece opened first and foremost. 3. Headline - The headline could account for 80% of your success. 4. Offer - A great offer can overcome bad copy. 5. Guarantee - Skepticism and fear stop most people from responding. 6. Postscript - Experts say its the second most looked at salesletter element. 7. Long vs. short copy - People want to know the detailsreally!   "Split A/B testing" is a common technique that direct mail marketers use to test their mail pieces. It includes splitting a list into two groups and sending one piece to group A (control piece) and the other piece to group B and evaluating response rates.   As for the second question, there are a number of ways to track the success of your direct mail campaign. The first step is to code your direct mail piece. You can do this by using different response telephone numbers for each piece, or by putting a code on the enclosed return form. This allows you to know from which campaign the response is coming, resulting in an accurate response rate count.   However, if you send a postcard or insert a coupon you could ask your recipient to bring it in to take advantage of your offer. I like to use one toll-free phone number with different extensions to track response rates.   I often place ads in different trade magazines and include unique extension numbers in each ad, which lets me know to which ad my customers responded. This saves me a lot of money because it gives me empirical data that shows me where I should be spending my precious marketing dollars.   Here are several rules to follow when testing your direct mail piece:   Rule # 1 - When testing, only make one change at a time. This isolates the difference, which allows you to conclude with some certainty that the tweak you made was the cause