CHICAGO (AP) _ Restaurants will be judged in the 1990s not by what they serve but how they serve it, experts said.

With more two-income families, people value time more and are unwilling to put up with second-rate service, insiders in the $200 billion-a-year industry said Tuesday at the National Restaurant Association trade show.

''People expect top-notch service even in fast-food restaurants,'' Dru Scott, a San Francisco psychologist who advises organizations on customer satisfaction, told about 100 restaurateurs in an address.

To survive, restaurants must use psychological tricks to keep the customer satisfied, she said.

''Think more of customer delight, not just satisfaction,'' she said.

That means using only positive behavior in negative situations. If a restaurant runs out of a certain item, the server should not say, ''We don't have that,'' but instead should offer something on the menu that is similar as an alternative, Ms. Scott advised.

If there's a long wait, give those in line menus to keep them interested. And if a customer complains, assure them that their comfort is your top priority, she advised.

Seek customer feedback to learn how to please them, and encourage employees to serve better by developing ''games'' such as keeping track of which server tallies the biggest checks for the day, Ms. Scott said.

John Iannotti, manager of Nick's Fishmarket in Chicago, said his restaurant has discovered the recipe for keeping the customer happy.

''Service is definitely our main priority,'' said Iannotti, one of thousands of restaurateurs who gathered at the five-day show.

''We want people to walk out of the restaurant commenting first on the service, and second on the food,'' he said.

''You really can't do that much with food'' to improve on another quality restaurant's menu, Iannotti said. Service is the variable that can determine if a customer returns, he said.

Service showed up as a top concern among consumers queried for this year's Yankelovich survey, an annual study of 2,500 consumers nationwide conducted for consumer-oriented industries by the Connecticut-based consulting firm, said Bonnie Schwartz, director of restaurant marketing for American Express.

''We're moving into a much more financially conservative decade, with intense competition for discretionary dollars, which of course forces services to become more attentive,'' she said.

American Express unveiled a program it calls the ''American Express Salute to Restaurant Service'' in which the company will give cardmembers certificates to award to restaurant staffers who give the best service. The staffer who gets the most certificates will receive $10,000 in travelers' checks.

The customer who gives out the most certificates will win a culinary tour to France, Ms. Schwartz said in an announcement timed to coincide with the restaurant show.

The nationwide contest runs from June through September.