As everyone knows, the most important thing to take along when one travels is a coat that can serve equally well as a raincoat, bathrobe, evening wrap and lap robe on airplanes. Miss Manners has never actually seen such a garment and cannot imagine what it could look like or be made from, but has heard of it so often from those who give travel advice that she has the deepest respect for it.

Should she every find one, she would certainly take it traveling, even if she had to plan a special journey to do so.

But that decision does not seem to Miss Manners to settle all the packing problems. A most perplexing one, for example, is how much of one's identity must one pack up and take along wherever one goes?

The two chief purposes of recreational travel, it seems to Miss Manners, are to meet new people and to abandon old ones. One can travel to do either, or both, and there are several variations, but in any case, it is an encumbrance to take along one's full identity. (this is equally true of the voyage taken for the purpose of fleeing justice, of course, but we are not discussing business trips.)

Let us begin with the second category, since that is generally what draws Miss Manners away from her smug hearth and circle of dear faces. If one believes that one's friends should always be able to find a sympathetic ear and a ready smile, one must occasionally air the ear and turn the smile upside down and shake it.

The last thing one needs on such an outing is a whole new set of acquaintances. One therefore tries to present oneself as being rivetingly uninteresting. You may say that this should be a cinch, but there is a trick to it.

This is because everyone sounds uninteresting on early identification -- and those who have perfected clever and unusual opening gambits confirm this notion. The idea, when hoping to travel incognito, is to be as unspecific as possible. Identifying one's home as the nearest large city, naming one's occupation as the commonets task it involves (such as "washing up" for surgery) and denying any knowledge of the origin or sharers of one's surname are baskc to discouraging professional, personal or geographical points of conversation.

You would think, then, that a person interested in establishing connections would only have to do the opposite. But, in fact, if you take the trouble to venture away from home and office to seek acquaintance, the chances are that you are bored with your natural sphere and hope to break into a new one. In this case, too, you would want to be vague about your present niche.

Miss Manners does not condone falsifying passports, or even oral identification to the curious. But she does not think that people on holidy are obliged to supply details about themselves that will enable others to get a true rendering of their proper place in the world.

You may notice that Miss Manners has suggested identical tactics to people with opposite goals. Perhaps she should supply a few directions, concerning the delivery.

If you want to be sought after in a strange place, you must give out your ostentatiously mundane biography with a guilty smile, an ironic twinkle and a confident tone of voice. It will be widely believed that you are a person of importance hoping to pass unnoticed, and your popularity will be assured. But if you deliver it with an eager smile, a hopeful eye and an anxious voice, you may hope to enjoy solitude in any crowd. MISS MANNERS RESPONDS

Q. I have a few questions about public dining:

Is it impolite to eat ice in public? How can it be helped if you have ice water?

When ordering a dish that requires a salad, is it insulting to the waiter or restaurant not to order the salad with your meal?

How about my arms, not elbows, but arms, on the table?

A. If you will sit up and stop louging all over the table, Miss Manners wil answer you first two questions.

What helps the problem of ice in ice water is time.

Miss Manners has yet to hear of a waiter or restaurant owner who has run into the kitche, put his head down on the steam counter and sobbed unconsolably because some mean person didn't order the salad.

Q. At what point in the decline and fall of a marriage is it proper to remove one's wedding ring?

A. Nature's way of signaling that a marriage is over is to change the wedding ring from a charming piece of jewelry into an unbearable dead weight. At that point, one removes it before it strangles one. If, however, you have this sensation while still fond of your spouse, perhaps you ought to lose some weight.

Q. Are punch cups a proper container for juice served to guests when enjoying hor d'oeuvres before dinner? If not, should I use regular juice glasses and save the punch cups strictly for serving punch?

A. Juice served with hor d'oeuvres is, by definition, punch, and should be served in punch cups. On the other hand, if one drinks a mess of different juices laced with alcohol for breakfast, one calls it juice and serves it in juice glasses.

Q. Our parents are going to be married 25 years as of this fall. My jsister and I want them to reenact their wedding, with bridesmaids and all the works. Would this be proper to do?

We are also going to have a reception afterwards. Would it be OK to mention on the invitations that we are having a money tree? After 25 years of marriage, they have everything a household needs, and we thought if we had a money tree, they could go on another honeymoon or do whatever they wanted to do.

A. After 25 years of marriage, they probably also have some sense, of both the common and social varieties. Since you do not seem to have consulted their wishes, please allow Miss Manners to express the sensible viewpoint.

Your parents may want to repeat their wedding vows, a charming ceremony, and they may want to have members of their wedding party and other friends at a reception to celebrate the occasion.

What they probably have too much sense to attempt is dressing up in the clothes of their yough to parody a young peoplle's wedding, and straining their old friendships by using a social event as a fund-raising opportunity.

Q. One of my lovers has the rude habit of interrupting intimate moments with me to answer his ringing telephone. Even worse is his inclination to then converse lengthily with the caller, usually a woman. He has engaged in this egregious habit during foreplay and during after-play. (I don't know if he is wont to interrupt during-play to answer his phone because, luckily, his phone has never rung during during-play.

I think that to be so easily diverted from intimacy is rude to the person with whom one is being intimate. I am made to feel as if the ringing telephone is more enticing than my company. I think ringing telephones should be ignored at certain moments. If the caller has something important to say, he or she can call back later. Also, the sound of the ignored ringing adds a certain je ne sais quoi to intimate moments. How do I cure my lover of this habit without seeming jealous? Or Am I allowed to seem jealous?

Please do not suggest that we conduct our intimate moments at my house, where I could control the telephone, because I live with another man and even more serious questions of etiquette would probably arise.

A. As you have asked Miss Mannners' opinion of your behavior and your friend's, she must tell you that both of you are guilty of extreme indecency.

No gentleman would give his attention to any telephone caller while he is entertaining a guest. And no lady would be able to identify such a caller as "usually another woman," because she would not have eavesdropped on the conversation.

As there are many complicated questions of etiquette arising these days from new patterns of behavior, especially in the category of courtship, Miss Manners would not have thought you would take up her time by going into such simple, old-fashioned, basic matters.

Q. Kindly tell me when and where it is proper to serve coffee in demi-tasse-sized china cups. How much coffee per demi-sized cup should be used? Should the coffee be served from a large silver urn, or a regular sized silver coffee pot?

A. The time to use demitasse cups (a redundant expression, you may notice) is after dinner, when nobody really wants coffee because then they won't be able to sleep, but everybody is too wide awake to go home. The service is done in the drawing room, never at the dining room table, and the amounts of coffee, sugar and cream offered are scaled proportionately to the cups. It is rather like a doll's tea party. So little coffee is required that an urn would be rather much, in Miss Manner's opinion, unless you invite a great many dolls.

Q. In a wedding reception line, is the bride's mother -- the hostess -- obligated to introduce everyone to the groom's parents? The groom's father is a doctor.

If the answer is yes, are the introductions formal, such as "Mr. and Mrs. John Doe, I would like you to meet Joe's parents, Dr. and Mrs. Brian Smith," or "Jane and John -- Joe's parents -- Brian and Ann," or "Dr. and Mrs. Smith -- Mr. and Mrs. Doe?" I know the basic rules, but this one is causing me to throw up my arms in frustration. The reception line is necessary because the groom's parents are from another state.

A. Bring down your arms. A receiving line is like a game of "Telephone" -- you need only pass the word to the person next to you who must, in turn, pass it to the next person and so on.

Thus, you need only say, "This is Joe's father, Brian Smith; Jane and John Doe"; and he is responsible for saying, "And this is my wife, Ann; Jane and John Doe." That is as informal as Miss Manners will let you get -- an introduction without surnames is not an introduction.