YOU HAVE all heard what dear Mr. Benjamin Franklin said about what happens to guests and fish after three days. He was speaking from that point of view of host.

Miss Manners will now address the problem from the point of view of guests and fish who would like to remain after three days but stink as little as possible.

The question comes up because guests and fish tend to hang around where it is possible for them swim. People who have beach houses or pools sometimes have bursts of generous hospitability, and it is in the interest of the recipients to insure their not living to regret this.

Anyone ought to be able to be a good house guest for that three-day period, which is why God invented the weekend. One's time is more or less planned, and one's hosts are able to sustain an act of graciousness and calm, postponing weeping over the antique you broke or barking orders at their children until the house is theirs again.

But longer periods require greater variety of emotion, and the considerate long-term house guest will assist in making his hosts feel at home. Otherwise, he will quickly find that he is.

The most helpful way of doing this is to plan frequent absences from the house. These should be announced in advance, so that there are no uncertainties about whether the guest should invent excuses and go off by himself, to give the family opportunities to cry, argue or relax in privacy.

If, however, unscheduled eruptions take place while the guest is present, the guest should ignore them and disapper. Under no circumstances should a guest take a side in family differences or offer suggestions for improving the family's way of living. All appeals for help must be resisted. Ultimately, nobody wants a family counselor, however sympathetic or fair, living in one's house and seeing to it that everyone behaves properly.

It should be unnecessary to mention that the house guest should create no additional work for the family. It is his obligation to keep the guest room clean, whether he likes it that way himself or not. Even behind a closed door, a guest room with an unmade bed or newspaper-strewn floor acts as a reproach to hosts.

The guest must share the chores -- but not by running about asking, "Can I help?" and taking no for an answer. By simple observation he should be able to notice what needs doing, and do it.

Preparing meals, cleaning up, babysitting, and occasional grocery shopping -- selecting what the family likes, and paying for it -- are activities that make a guest seem worth keeping.

So do little presents, given at perhaps the rate of one a week. A house guest is in an excellent position to notice what might be appreciated, and it is nice to associate presents with one's presence, not just with one's long-awaited absence.

But the best present a guest can make after he has left is his silence. This must consist not only of the wonderful silence that pervades the house when he leaves, but his own precious silence in refusing to divulge the family secrets to others. MISS MANNERS RESPONDS

Q. Now that the summer heat is upon us in full force, you simply must help us down here in Charlottesville by answering a rather perplexing question. Which is more proper, to eat ice with a spoon, or with a fork? Please don't tell us that it is not to be done because eating ice as an appetizer has become all the vogue here lately. I was under the impression that it was acceptable to eat ice with a spoon, until I was informed rather coldly during dinner that correct way of transporting ice from one's water glass to one's mouth is by means of a fork. Please, Miss Manners, will you tell us which mode of ice eating is preferred?

A. Why would you think that Miss Manners would disapprove of ice as an appetizer? What else is so low in calories, violates nobody's special diet restrictions and harms no one's budget? If ice is served in a water glass, one drinks the water first. Then one tilts the glass until the ice hits one on one's nose, which is very refreshing. The glass is then lowered with the ice at its edge, and the ice is allowed to enter the mouth.

By this method, neither spoon nor fork is necessary. If you feel you must fish ice out of a glass, however, do it with an iced-tea spoon. The sight of a hand in a glas up to the wrist, trying to get an ordinary teaspoon to the bottom, is not pleasant and sometimes not easy to remove from the glass. tIce, particularly when it is melting, is not eaten with the fork.

It is not considered good manners to gnaw on ice sculpture that is used as a table decoration, nor to break off parts, such as snapping the neck of an ice sculpture swan to get the head.

Q. My beau and I have been asked to be weekend guests by his friends in another town. These friends do not smoke, nor does my beau. his friends do not permit smoking in their house. I am a smoker and have refused to go because of these circumstances. If the invitation had been for dinner only, I could oblige by not smoking, but a weekend is impossible. Do you think my behavior stubborn or justified?

A. Both. An honest person cannot accept hospitality with the intention of disobeying the house rules, and yet you have been startingly honest with your beau about what your greatest pleasure is. A little less honesty -- whatever happened to sneaking out at night? -- would have been more tactful.

Q. I am writing to you for assistance in dealing with a modern social entity -- the former live-in (not domestic help, although that may have been a part of the arrangement).

My husband of a year-and-a-half and I live in a small town. His former live-in resides here as well, and small towns being what they are, we travel in the same circle, which means we encounter her at least every two weeks at one gathering or another. Although she currently has a new attachment, it is my strong feeling that she still cares deeply for my husband. For the most part, I can handle the situation rather gracefully; however, there are occasions where my strong inclination is to punch her in the nose, offer her a handkerchief and walk away.

Let me explain.

At a gathering, she told me that she had to talk to me, spirited me away from the group, and proceeded to deliver an extended and detailed monologue on her last days with hubby. Those days were close to three years ago. I listened graciously and sympathetically and spent the night at the local Holiday Inn, because I was unable to bear the sight of hubby, an unfair transference, I realize.

Her latest escapades, however, are causing me greater distress because they involve my in-laws. Of late in her monologues she has taken to referring to hubby's mother as "Mumsie." Most recently, she went shopping with Mumsie and hubby's sister, spending the night in the city at Mumsie's apartment. The whole expedition left me rather stunned, particularly as it was described to me in great detail in yet another monologue which included a listing of presents purchased by her for hubby's family.

Hubby tells me I am being foolish to let all of this bother me. He suggests that I merely walk away when the monologues begin. He further says that I shouldn't be angry with him about the situation, since there is nothing he can do about it.

I have countered by saying that I can't walk away because the FLI (former live-in) will know she is getting to me, which would be more unbearable than the present situation. As far as being angry with him, I explain that what I am really angry about is the fact that his taste in women was so distressing until he met me.

With this background, let me ask my specific questions: 1. How can I deal politely and effectively with the Fly's monologues in order to put a stop to them? 2. How do I cope with in-laws who show such insensitivity to my feelings in this rather delicate situation?

A. Do not -- repeat: not -- punch her in the nose. This will be correctly interpreted as her having "gotten to" you.

Be polite. Ignorant people often define etiquette as simply "making others feel comfortable," not realizing that it is often the only way to make others feel uncomfortable.

Tell the FLI and Mumsie, as often as you can, that each is terribly kind to "take care" of the other. This always convinces people that they have been stuck with bores.

Then tell the FLI how very amused you are by all these stories; how you love hearing about your husband's bachelor adventures, which he can't tell very well because he's forgotten so much and keeps mixing up the characters. You might ask her if she was the one he took to the Riviera.

He needn't help much, but it would be nice if he would interrupt these tete-a-tetes to greet his old girlfriend heartily by the wrong name.

Q. My husband and I disagree on how to respond to a frequent demand: We live in the city and own a small car that we use only when very inconvenient not to do so -- for example, to attend parties in the suburbs. Almost inevitably we are asked to give other guests without a car a lift home. Unfortunately, these are usually the people we've enjoyed meeting the least. Although this is really no big inconvenience, we feel as if we cannot refuse; our freedom to leave when we choose or to stop en route home is hampered.

Can we politely refuse these requests? If so, how? Or are we being mean to even think of refusing?

A. Well, you are being as tad selfish by bragging about how little you use your car and then to wanting to help others cut down or out on the use of cars.

It is not that hard to accommodate others without giving up your freedom. It is, after all, your car. You could say, "We'd love to give you a ride -- we'll be leaving in probably about another hour," thus leaving the petitioners the choice of waiting or of seeking earlier or later departures with others. Or you could say, "Certainly, if you don't mind waiting while we stop for a snack on the way home." Flatly refusing to give people lifts is the privilege only of people whose cars never break down.