SHOW MISS Manners a grown-up who has happy memories of teen-age years, with its endless round of merrymaking and dancing the night away, and Miss Manners will show you a person who has either no heart or no memory.

Dances for the young were surely not intended to be lighthearted. That is probably why nature always insures that the couple who enjoy them most -- the most popular girl in the prettiest dress matched with the most popular boy in the best car -- always come to reluctant early parenthood, poverty and piggishness of appearance.

Those who hope to lead pleasanter lives must endure the ritual of young social agony. To those who have missed out, for lack of invitations, Miss Manners offers the comfort that they are getting off easily, and that confessed unpopularity in childhood is an endearing trait in an adult.

If the dance is to be attended in pairs, the rules for ordinary dating apply: The gentleman makes a specific offer for the occasion, with some warning, and the lady can accept or refuse. The difference between a private date and a public dance is that if she plans to show up with whoever asks her next, the wording of the refusal had better be ambiguous.

More than in general dating, the custom prevails of having the gentleman call for the lady. He also assumes responsibility for her being pleasantly occupied for the evening, claims at least the first and last dances, and fetches her food and drink or accompanies her to get it.

The return responsibility is that the young lady undertakes to occupy herself for much of that time, even if she is reduced to engaging the chaperones in animated conversation.

Miss Manners misses the dear barbaric days when ladies had dance cards on ribbons at their wrists and could schedule their evenings. If juggling one's admirers didn't tax the strength, then inventing names taxed the imagination.

The request for a dance is correctly worded, "May I have this dance?" Miss Manners would advise a young gentleman not to adopt the alternate wording, "Do you want to dance," that suggests the answer, which Miss Manners hopes would remain unspoken, "Yes, but with not you."

Acceptable answers to the former, correctly worded offer are: 1. "Why, yes, how delightful." 2. "I'm so sorry, I promised this dance already." And 3. "I'm just too tired to dance now." One cannot hop up on the floor with someone else after offering the third excuse, but there is nothing to prevent one's taking another companion for a bit of refreshing air or punch during that time.

Unless cutting in is against the local custom, the procedure is for a young gentleman to tap an engaged young gentleman on the shoulder and spirit away his partner; the second young gentleman is not allowed to offer to tap the first on the nose for his trouble.

It is a long-established custom on the part of young ladies to encourage cutting in by delivering a soft look over an alien shoulder to the prospective cutter inner. Waves of distress, however concealed from the object of that distress, are not permissible.

You will notice that proper behavior encourages opportunities for disaster by having the participants mix and socialize, rather than stay safely anchored to the secure date, however dreary. Like all social customs, this has a purpose. It makes adult social life seem simple and carefree.

MISS MANNERS RESPONDS

Q. I was startled and no little appalled when, at the conclusion of a recent lunch, a friend who is normally in the best of taste placed her napkin atop the remains of food on her plate. In the discussion that ensued, another friend opined that leaving a paper napkin on one's plate was proper, while placing a cloth napkin there would be incorrect.

I do not believe that such an action would ever be acceptable. Please advise us as to the rule in this case. Since restaurants insist on providing paper napkins these days, if there is a distinction based on fabric, it would be useful to know.

A. Miss Manners' friends of the Victorian era were much ridiculed in later periods for refusing to recognize aberrations of behavior. Those who ridiculed failed to appreciate the wisdom of saving oneself the trouble of dealing with difficult matters by refusing to acknowledge that they exist.

Miss Manners refuses to acknowledge paper napkins. The place for used napkins is beside the plate.

Q. What is the proper equipment necessary to eat snails? And then, how do you use it?

A. Surely you mean to ask: What is the maximum equipment you can use to eat snails, and how can you make the beggest fuss and have the most fun doing it?

Snails, after all, may be prepared in many delicious ways and served in a sauce on a plate or on toast this is, in turn, on a plate. All you need then is a fork, and some dexterity in cutting the sodden toast with the edge of the fork.

To make the most of the dish theatrically, and still have something slurpy to eat, you can buy snail plates, tongs and forks, hide the snails in shells to give them a sporting chance, and then attack them with both hands and all this metal.

The snail plates are ceramic or metal, with indentations for the snail shells, in which are put the snails themselves, usually floating in garlic butter. The whole mess has probably been broiled as a unit, so slyly steadying your plate with your fingers, never proper, is promptly and severly punished.

Snail tongs have a bowl that opens when you press the handle and then closes around the snail shell, anchoring it. The fork is narrow, with two prongs that pierce the snail and drag it out of its lair. As the tongs are held in the left hand and the fork in the right, it is permissible to empty the shell of its sauce over the extracted snail.

Now comes the real conflict of the conscience. As you know, Miss Manners does not approve of sopping up sauces with bread. However, she approves of garlic butter. That is why you see her turning discreetly away from you at the table, and also why you hear her offering to clear the snail dishes from the table.