The best way to test your product is to share it early and often with potential end users. That's what the software company Intuit,in Menlo Park, Calif., has done, and it's given the company domination of the market.

Intuit makes Quicken, the check-writing and financial-record software. In 1994, the company had revenues of $223 million.But back in 1984, when Intuit founder Scott Cook was starting out, all he knew from telephone research was that people wouldbuy check-writing software only if it were faster and easier to use than a pencil. To test a prototype, he and the company's chiefprogrammer, Tom Proulx, brought together a group of Junior League members. They did fine filling out the check outlines ontheir computer screens, but when it came time to print, they fumbled; the checks printed too high or too low. Cook and Proulxcringed. "We knew one thing," recalls Proulx, now retired. "If people had that much trouble the first time they used theprogram, they'd never use it again."

The company fixed the problem and continues to test relentlessly. One testing method, called "Follow-Me-Home," has Intuitrepresentatives observe new users when they first use the product. "You watch their eyebrows, where they hesitate,where they have a quizzical look," says Cook. "Every glitch, every momentary hesitation is our fault." The testing helps thecompany figure out which areas to work on each time it updates its product.