What great fun it is for those of us old enough to appreciate nap time to imagine wild free youth out there overflowing with exuberant emotions and happily struggling in vain to suppress the madcap ways they keep inventing to express them.

Unfortunately, however, the real chief social problem of youth is the habit of standing around looking stupid.

Mind you, Miss Manners is not accusing anyone of actually being stupid. Tuning out of conversation that does not immediately concern one, responding minimally to banalities and utterly relaxing the features whenever possible, short of allowing the tongue to loll outside the mouth, may be defended as rational behavior.

Children who have been encouraged all their lives to act natural (although the admonition does carry a certain curious contradiction) quite naturally turn to such expressionlessness once they have outgrown their bounciness.

But standing around looking stupid is an extremely impractical social posture.

Adults invariably interpret it as representing stupidity, or at least contempt for themselves, which they naturally believe to be the same thing. It is not a wise idea to leave this impression on adults, not so much because they have feelings but because they have beach houses, summer jobs to give out, places in schools to allot and the ability and opportunity to air damaging opinions in front of their own children.

Even adults who have a vested interest in believing these expressionless children to be miracles of cleverness react badly when they see it. A happy, active child is generally smiled upon by its parents; one that is hanging around looking stupid inspires them to request that he study, take out the trash, practice or get a job.

Standing around looking stupid is also a handicap for the young among people their own age, however much these people may practice it themselves. The new kid in school or the neighborhood and the stranded person at a party or dance, who may well be standing around looking stupid because he or she quite properly feels stupid in such a difficult situation, arouse scorn rather than pity.

So you see, it is really a dreadful idea.

The alternative is to act some other way: cheerful, attractive, amused, interested, absorbed, confident or as if one knew what one were doing.

Different expressions are appropriate for different occasions. The general idea is to anticipate the reaction you wish to get from the other person by simulating the feeling you want. In other words, you act interested if you hope someone will find you interesting, confident if you want someone to give you an acceptance to school or job that would build your confidence and popular if you wish to win the friendship that would make you popular.

Miss Manners is not claiming any of this is easy. Acting is a difficult profession, although an interesting one. Contrary to the popular notion that it just comes naturally to people born with talent, even the simple ability to observe, interpret and reproduce the physical manifestations of emotions requires a great deal of intellect and work.

And the least stage-struck person must master a bit of this in order to dramatize his own real emotions or the ones he wants to display, just enough to convey them to other people in his life.

The intelligent-looking face is therefore always alert when other people are around, as if capable of registering what its owner hears and sees. It need not be grimacing wildly, but the eyes should be in focus and the mouth in a state to be mobilized instantly for talk, laughter or whatever.

One should then learn basic responses, such as smiling upon greeting people, nodding occasionally when they talk, laughing when they look as if they have told jokes, appearing to be pleased when they show interest by asking silly questions and so on.

The clever young person will understand that the fact that he has reason on his side for looking impassive at seeing these people, daydreaming while they talk, remaining immobile at their humor and bored by their questions has nothing to do with it.

One is not only being polite to them, regardless of their claim on such an effort, but practicing being charming. As the charming person has a marked advantage in life over all others, even those of decidedly more important virtues, it is a skill worth honing.

And the first requirement of charm is that the bearer of it appear to be alive.

Q. My husband and I were invited to my friend's house at 5 to eat, but my husband came home from work at 4, starving.

He wanted me to call her and see if we could go over then, but I wouldn't. How would you have handled this?

A. With a sandwich.