When Americans eat out, they want a clean table

What do customers expect when they walk into a restaurant? They're looking for all the usual, predictable things such as good value for their dollar, good service, and top-quality food.

But most of all, according to statistical surveys by the National Restaurant Association (NRA), they want and expect cleanliness. It's a quality NRA officials admit is hard to define and almost impossible to promote.

''Customers will stop coming to a restaurant if it's dirty, but they won't go to it just because it's clean,'' says Susan F. Mills, the NRA's director of research and information services. ''I think cleanliness is largely a matter of in-house discipline. You have to keep wiping up, mopping up, and brushing up, because you don't know who might come through at the wrong moment.''

At the NRA's annual meeting here, Ms. Mills stressed to restaurateurs the importance of thinking of the customer's needs and expectations in everything from menu design to the choice of a promotion tack.

For example, she advised restaurant managers to quiz waiters on what people are asking for that is not already on the menu. And instead of billing a light item as ''low calorie'' or ''diet,'' she suggests words stressing quantity and satisfaction such as ''piled high with yogurt'' or ''topped with sprouts.''

To keep a restaurant's name before the public, Ms. Mills says eating establishments have tried every gimmick. These range from the clever to the deliberately ridiculous, and they often get very positive results. Here in Chicago, Grover's Oyster Bar has a shuttle bus that boasts, ''We brake for shellfish.'' This tactic, Ms. Mills says, amounts to a mobile billboard.

She recommends gearing promotions to special events. But she warns that free and discount coupons can become ''destructive'' to restaurateurs, if customers become too dependent on them