RESPECT your elders" was always the favorite etiquette rule of the adult population, which has unaccountably allowed it to fall into disuse. It is surely the rule most regretted by parents who neglected to teach it to their children.

Actually, Miss Manners never quite liked it in exactly that form. To claim, even to the smallest children, that all adults are worthy of respect seems to her unsupportable without an unusually difficult effort to falsify the evidence.

The rule that she prefers is, "You must treat all adults with respect."

You see the difference. Manners wisely do not attempt to regulate the thoughts and feelings of those they seek to govern. They restrict themselves to demanding proper behavior.

It is reasonable and wise to require children to address adults with the appropriate formality of family title ("Aunt Candy") or civilian rank and surname ("Mrs. Heppzapittle"); to expect them to rise when adults appear; to refrain from beating them to a seat on the bus and to surrender one when in possession; to answer their questions and remarks civilly, even if they are silly or repetitive; to restrain themselves from inappropriately pointing out their errors and from analyzing what powers could produce such errors, and so on.

It is neither wise nor reasonable to expect children to think that adults are, by definition, smart, right or admirable. Such an attempt will quickly lead a child of even average powers of observation to the conclusion that at least one adult, the one who makes this claim, is either dim-witted or mendacious.

It also takes all the fun out of observing the adult world. A child who is never allowed to betray the belief that any adult has done anything wrong is one who will quickly lose interest in the idea of being among such deluded fools.

On the contrary, Miss Manners recommends encouraging critical discussions of outside grown-up behavior in the privacy of the family. It is the reward for having restrained oneself while these people were present.

It also teaches both manners and charity.

A child who can delight in watching an adult misbehave, and receive confirmation later that the conduct, which was politely allowed to pass without comment at the time, was noted, will pride himself on the superior practice of good behavior.

At the same time, he should be taught that judgment is no easy matter. People who, although ignorant perhaps of etiquette refinements, have hearts of gold or other redeeming qualities should be duly credited.

Most importantly, the child who learns to observe the adult world as complicated theater, which he gets to help critique, will have the incentive to enter that world.

If he is permitted to have polite arguments and discussions with the appropriate adults--parents, other fond relatives, teachers--based on critical observations of the sophisticated world, he will have an interest in the ways of that world, and a desire to participate in it.

The credentials for doing so are being able to know what is right and what is wrong, and at the same time to develop the skill of politely pretending that one sees only the right. A child who can do that may be trusted to get safely through his parents' parties, college interviews and life. MISS MANNERS RESPONDS

Q. My cousin intends to be married soon. He and his fiance'e plan to invite only married cousins, rather than all cousins, to the wedding. I am single, as are most of my brothers and sisters. This arrangement would, therefore, exclude most of my parents' children. This offends them and me. Would you please comment on this rather unusual form of discrimination?

A. Having just advocated keeping wedding guest lists down to size by using apparently arbitrary categories, Miss Manners finds herself in an awkward position. She has gone on record as saying that it is less offensive to exclude certain people if one can find a rule to fit them (no third cousins once removed) than it is to ban certain eligible individuals.

But this is ridiculous.

If no single people are to be admitted to the wedding, the bride and bridegroom would be ineligible. Besides, weddings are famous for being charming opportunities to begin acquaintanceships that blossom into other weddings, so it seems a particular hardship to exclude the single people; the married people can always use the extra time to straighten up their households.

However, Miss Manners was not consulted, in this instance, by bride, bridegroom or their parents, and neither, she gathers, were you. The proper behavior for all of us, therefore, is to sniff among ourselves about how badly this was handled, and yet show no indication of displeasure nor register any complaint.

Miss Manners doesn't know about you, but she can face this task with perfect equanimity.

Q. My friend Dodie has been divorced for two years, and she is quite desperate to meet men and to make new friends. She'd been asking to meet my friend Joe for about two weeks, so I arranged a dinner. She works 10 hours a day and commutes another hour home, and has to be on call on her night off.

At first she said she just couldn't do it. She had to stay home by the phone. Why didn't we come over for a drink? I said I had asked a date for myself, too, and I wanted to make Mexican food. Why didn't she forward her calls to my house? She said okay.

She asked what she could bring. I said salad.

The night of the dinner, she said she hadn't gotten home in time to go to the store, and that she was extremely worried and pressed, and would it be all right if she didn't stay very long? She said she had put the "call forward" on, and I was not to answer my phone until she arrived.

Meanwhile, I trudged to the store to get last-minute salad fixings. Dodie called twice to make sure I didn't answer the phone.

When I introduced her to Joe, she barely said hello and started talking about: 1) being worried that she couldn't hear the phone if it rang; 2) how much she had to do that night; and 3) how she wouldn't be able to stay long. The two men sat in the living room, but Dodie stayed in the kitchen with me and stewed over the pressure she was under. She kept saying, "Are you going to be mad at me if I leave?"

I was furious. I felt like I had gone to some trouble, at least, to introduce her to my friend. Fortunately, another friend called, and four more people came over after dinner. We had a great time, and her absence was forgotten.

My questions are:

How do you explain behavior like this to your other guests, or should you?

When asked to bring the salad, should a guest bring the salad come hell or high water?

If you have other things on your mind, should you decline a social invitation?

If you have other things on your mind and you accept the invitation, should you forget the other things on your mind and not bore other people with them?

Last, what should I think about this friend?

A. Miss Manners believes in thinking charitable thoughts about one's friends. Let us assume that Dodie is so terribly overwrought, from business or social concerns or a combination, that she is not herself. This assumes, of course, that when she is herself, she has manners, and when she resumes being herself, she will apologize to you in the most abject way.

You will be happy to hear that such charity does not extend, in Miss Manner's opinion, to not being furious at such behavior, or to entertaining such people. Let us say that we will kindly refrain from adding social engagements to her already unbearable burden.

Now for the earlier questions:

You properly explain such behavior with a shrug and a short apology which does not condemn one who was, after all, your guest. "I'm terribly sorry--poor Dodie is really not in a state to enjoy herself, and I was wrong to press her to come."

The offer, "What should I bring?" should never be made unless one is willing to undertake a reasonable request (you did not ask her to bring Baked Alaska); it then becomes binding.

No, you don't go out if you can't be polite company, and yes, you must disguise your problems if you do go out.

Miss Manners is pleased that the evening finally turned out well. Joe wouldn't have liked Dodie, anyway.

Copyright (c) 1983, United Features Syndicate, Inc.