It's a generally accepted rule of direct marketing that the more targeted your campaign, the better the results. However, it's not so much the raw number of responses that matters for most companies as much as the cost per lead. While you can always eke out a slightly higher response by tailoring your campaign to a particular audience, the small increase may not always merit the extra expense.

A good example of this is so-called "vertical" campaigns - that is, programs that target a particular industry, say manufacturing or financial services. On the surface, a vertical campaign makes sense, because the more your creative speaks to the particular pain points or benefits relevant to a particular type of company, the more it will resonate with that audience, and the more they'll respond.

But there's a price to pay, and that trade-off comes in two categories:

First, lists. Whether you're planning a direct mail or an e-mail campaign, it's only a subset of the total list universe that will make available selects (ex: SIC codes) that enable you to choose names from a specific industry. Then, even if a handful of lists offer those selects, fewer still will have sufficient names in their database from that one industry to meet the minimum order (typically 4-5,000 names).

More than likely, you'll end up having to either 1) choose vertical trade publications which typically don't offer other critical selects (job function, company size, purchase authority, etc.), 2) opt for large, compiled lists that offer plenty of names from your target industry but don't perform well, or 3) drop key selects (like those just mentioned) in order to meet minimums.

Secondly, cost. It you target multiple industries simultaneously, you'll pay a premium - in creative and production - to "version" your campaign (whether print or online) for more than one audience. (The cost difference is greater for direct mail than e-mail, where production issues are largely irrelevant.) In practice, we find the incremental cost usually isn't matched by an equivalent increase in response.

Here are two tips to remember for making your vertical strategy a success:

• One, tailor your offer along with your creative. One very successful recent campaign for a software client offered a CD-ROM that included case studies and sample applications from clients in their target industry.

• Secondly, include a "generic" version of your creative for names that fall outside of your target industries. This avoids the trap of having to meet minimum orders by compromising on key selects, and will give you a benchmark against which to measure whether a vertical approach really pays for itself.