"I had the most wonderful meal of my life last night," announced a friend who wanted to savor the joys of crown roast of lamb and rhubarb pie.

"It was a good dinner party?"

"No. It was a good meal. It was a terrible dinner party."

Food and wine are not the only pleasures of the table, as many a cook has discovered when one tasty tidbit after another fails to revive a dying evening. There must be conversation and that is as much the responsibility of the host and hostess as is the gallantine of duck and 1961 Bordeaux (though many, when offered the latter, would feel themselves well entertained by a recital of the ABC's).

French jurist, writer and gastronome Brillat-Savarin--who thought a great deal more about food and the people it goes into than most men--wrote, "Let the number of guests be no more than 12, so that conversation may always remain general . . . Let them be so chosen that their professions will be varied, their tastes analogous, and that there be such points of contact that the odious formality of introduction will not be needed . . ."

Writer M.F.K. Fisher, another connoisseur of what to eat and who to eat it with, would cut the dinner party down to six people, "No two of them should be so much in love as to bore the others, nor . . . should they be carrying on any sexual or professional feud."

Whether the ideal is six, or twice six, is less important than the thought that goes into the decision. Explains a Washington hostess, who also prefers six:

"The conversation remains general and everyone is part of it. Nothing is more infuriating than being trapped by your dinner partner in an intense, dull conversation when you can hear the guests at the other end of the table talking about exciting things. You're at the dinner, but you're not at the party."

"I prefer smaller dinner parties so that the conversation can include everyone," says a man who entertains frequently. "I also find that this is much more likely to be the case if most of the guests know each other. There should be one or two new people for variety, but if you have a dinner party where most of your guests have never met, they'll spend the whole evening groping around trying to find something in common."

"Giving a good party is like staging a play," says a man who does both. "You set the stage, choose the cast and, if things are going smoothly, you keep your hands off. If they're not, you step in to pick up the tempo.

"The only difference is that the first order we give to actors and actresses is 'Don't eat the props.' "

The woman who prefers dinners for six says that whenever she expands the table to eight or 12, she appoints a lieutenant to cover the other end of the table. "Conversation tends to splinter and it's important to have someone at each end to keep it moving."

Says another hostess, "Some evenings people are just too tired to sparkle--particularly Friday night, which I find is a very bad time to give a dinner party. People suffer a psychic collapse. But if you invite at least one guest who can always be counted on to perform, tell interesting stories, start an argument--anything--then the dinner party won't be flat.

"You're the one who knows all the guests. You're responsible for putting the right ones together. It's not just the obvious, like never seating a Zionist next to a Palestinian refugee, but subtle things like seating someone who never stops talking next to a good listener. You have to think about these things beforehand.

"I make up a seating plan, jiggling the names around until I think I've seated everyone next to someone they'd enjoy talking to. A guaranteed way to have your dinner party sink is to tell everyone, 'Oh, sit wherever you want.' "

If lack of planning can doom a dinner party, so can too much planning.

"I really like to eat," says a woman whose hobby is reading cookbooks, "and I have a friend who is a fabulous cook, but I hate to be invited to dinner at her house because she works herself into a frenzy. She cooks steadily for two or three days, and there is no way the guests can project enough appreciation to make up for all her effort. By the time they arrive, she's exhausted and irritable.

"All she wants is to be handed the Pulitzer Prize for cooking and allowed to go to bed."