Many businesses are launched on a hunch about a market for a particular product or service, but just because your hunch pans out and sales take off, don't assume you know who your customers are and why they are buying. You may be missing out on opportunities to keep the business growing in the future.

In 1979, Marjory Williams launched SHE/Laura Caspari on a hunch that women professionals would flock to a store catering to their particular clothing needs. After a year of healthy sales, however, Williams wondered if her first store, in Edina, Minn., was really attracting the people she had set out to serve. So she began asking customers to fill out a simple, photocopied questionnaire about themselves, their families, and their jobs. (Williams subsequently added questions about fashion preferences.) To ensure confidentiality, the customer could seal the questionnaire in an envelope and slip it through a slot into a closed box.

The survey confirmed that Williams was reaching career women. More important, it allowed her to identify new market niches -- petite sizes, for example -- and changing tastes. Williams believes that the survey also builds loyalty. "The message is 'We care who you are and what you want."