The important thing about giving a dinner party is that you have time to take a nap beforehand, says frequent party-giver Margot Hahn, who for the past three years has given classes in at-home entertaining.

"A nap with whom?" one of her students once asked. "That's up to you," she told her.

Hahn, whose lawyer-husband Gilbert once headed the D.C. City Council, prefers small dinner parties for 10 to 12 -- preferably seated "thigh-to-thigh at a round table" because "it's more fun" than if guests are 4 feet apart.

In her weekly morning classes, given at her sprawling ranch-style home perched on a hillside in a secluded Spring Valley neighborhood, Hahn emphasizes advance preparation. Getting as much done before, she says, means the host or hostess at partytime is rested and doesn't have to pop up constantly to check the kitchen.

Hahn teaches her classes in bare feet. "It makes me the right height for the counter." Her kitchen, with two separate sinks, is large enough to seat a group of 12 around a table and still not cramp her working space.

For a Saturday party, she says, advance work may mean setting the dining-room table on Tuesday -- "even if you have to eat in the kitchen the rest of the week." Use a bowl of fruit instead of flowers for a centerpiece because it's easier to arrange and doesn't have to be left to the last minute.

At a recent session, Hahn offered her students -- none of whom, it at least appeared, would be a stranger to formal entertaining -- a menu and tips for "a seated dinner for eight on a cold November night."

If everything goes properly, she maintains, the host or hostess should be able to get dinner on the table by spending no more than seven minutes in the kitchen after the guest arrive.

She began the lesson with dessert -- steamed pears stuffed with almonds in a raspberry sauce -- and the kind of near disaster than haunts the host or hostess hoping to make a good impression. When she reached for the almonds, which she had toasted ahead of time, the bowl was empty.

"The dog must have eaten them," she said. "Or maybe it was Gil."

"You should be prepared for a nightmare like that," said Hahn, not missing a beat as she reached into the cupboard for more almonds, "so buy double."

The pears are served chilled. "Recipes that say 'serve chilled' mean you have to prepare them ahead," she says.

Her main course, because it could be prepared days in advance and stored in the refrigerator or freezer, was beef stroganoff. If there were any raised eyebrows among her students, she quickly lowered them.

"Stroganoff has been out" as party fare "so long, it's back in again -- in my book anyway."

Pies, she adds, also have been out for so long that they, too, are back in again. "So serve lots of pies."

The principal ingredient in stroganoff is filet mignon, and Hahn says to assure yourself a good cut, "Cultivate your butcher. If you get to know him, he goes out of his way to be nice to you."

Do the unusual, she suggests. "Don't always have elegant foods for elegant dress." Instead, serve stews and goulashes. "It relaxes stuffy dinner parties." Save the fancy foods, as a turnabout, for a jeans-and-sweater night.

Never attempt last-minute dishes for a party such as steaks or lamb chops, Hahn cautions. "You end up splattering your best dress, and that's dumb."

Her first course was terrine of sole with dill sauce, a combination of frozen fish, spinich and whipped cream that can be prepared two or three days ahead and served chilled from a mold just before the guests sit down to eat. She mixes the ingredients in a food processor, which she uses often in her cooking.

The terrine, she says, "takes five minutes in a processor and days without one."

The rest of her cold November menu, which was not demonstrated, includes buttered noodles, watercress salad, hot sourdough bread, sweet butter and a dry red wine.

"I teach what I like in my kitchen. What you don't like, you have to drop out." Hahn's six-session classes have been offered five times a year by Mount Vernon College, but now she says she's got waiting lists.

For students who can't help noticing, she explains, "I do put my fingers in the food, and I must."

Cooking, she says, "is adult sandbox. If you don't get your hands in it, it's not much fun."

Hahn offers these additional entertaining suggestions:

Always serve white wine at a buffet. "If the guests spill, you can't tell." And get your spouse to tend bar.

Go easy on the hors d'oeuvres. "I serve one hors d'oeuvre, and I don't let them (the guests) eat much," especially "when you've knocked yourself out for dinner."

Tidy up the edges of a serving dish right after filling it. "Slops on a platter make the food taste terrible."

Lie if you have to. "I can't make chicken as good as Roy Rogers', and I never will." So she serves his and tells her guests, "I did it."