There's a well-known Silicon Valley company that fires the lowest-ranking ten percent of employees every six months. Though we're not an advocate of this approach as HR policy, you can apply the same aggressive posture to your direct marketing campaigns as a way to improve effectiveness over time.

For example, when marketing to an in-house list of customers or prospects, most companies mail or broadcast to the entire list and measure results en masse. Instead, it makes more sense to code your list based on demographics, lead source (where the person came from), age (how long he or she has been in the database), etc. and measure response accordingly. That way, you can determine not only which segments are performing best, but also which groups may not be worth your precious marketing dollars.

You may find that customers who bought from you more than two years ago respond so poorly that they're not worth mailing to. Or that prospects from trade shows are ignoring your e-mail newsletter. Eliminating these groups from future programs will help increase your marketing ROI by lowering cost and improving overall response.

When renting outside lists, split the names within each list based on job title, company size, or other select criteria (this is known as an A/B split) and then either code the names separately or send each group to a unique URL. You may discover, for example, that response from specific geographies, or companies of a certain size, or certain job titles, falls well behind the pack and that you can improve the effectiveness of future campaigns by deleting these groups from the mix.