IT IS not the junk mail from business concerns that Miss Manners minds so much as the junk mail acquaintances send out this time of year under the impression they are reconveying good wishes for the holidays.

The Christmas card, or the ecumenical holiday season card, is a fine institution if properly used. The custom of taking time, at the end of the year, to keep in touch with those whom one does not ordinarily see or write to, is a charming one.

However, signing one's name to printed inanities, or mimeographing a composition in which one brags about one's petty triumphs over the year, is not keeping in touch.

Keeping in touch means writing one's sentiments with one's very own hand. These may be a full letter, or only the words "Merry Christmas," but one must write this oneself.

At Christmastime, there are many different types of paper and cards that may be used for thsi purpose. Miss Manners, who is ordinarily strict about the colors of papers and inks, gets giddy enough at Christmas to enjoy the use of red or green, in inks, borders of cards and linings of envelopes. She would even allow pictures in good taste, which may sometimes include those of one's own family.

To those who feel that the Hi-There Greeting Card Co. has perfectly captured their feelings in one of its limericks, Miss Manners will only add the requirement that they nevertheless write out a message, however brief, between the posy and the signature.

Now comes the question of to whom these cards should be sent. The Post Office is obviously straining beyond its powers already, just trying to deliver people's Social Security checks, so perhaps some restraint should be used.

Miss Manners considers it superfluous to mail holiday wishes to those whom one offers such wishes to face-to-face, although one certainly may if one wants to. At the other end of the list, she suggests crossing off people whom one would no longer recogneze if they fell over one on the street.

What remains are the people one actually knows and likes, but cannot see or write to often during the year because of problems of time or distance.

It might help to consider the extent of such peoplehs interest. In some cases, they might find it sufficiently pleasant just to know that they are remembered. In others, there may be an eager audience for family news.

It is unlikely, however, that anyone's interests extend to three pages of single-spaced purple mimeographing. Furthermore, such Christmas letters are usually highly biased bits of reporting, rerely containing the sort of juicy news that is real general interest. They tend to run to the children's new teeth, rather than Mommy's new lover.

The final word Miss Manners offers on the subject of dignity in Christmas cards is the plea that they be properly addressed and properly signed. This rules out the use of such catch-alls as "and family"; if you can't address people by their proper names, then you address the card to those whose names you know, asking to be remembers you know, asking to be remembered also to "the children" or "your father."

The signature on a Christmas card should included a last name, and the envelope a return address. The only excuse for leaving them off and thus forcing your friends to play guessing games, is the hope that the mystery will encourage them to drop you from their list before you drop them from yours.

Miss Manners Responds

Q: Is there a correct form for resigning from a club?

A: Yes, but it is only useful when one is resigning for some simple reason, such as moving out of town or realizing how much the one lunch a season one eats at the club is actually costing when the annual dues are figured into the bill. This letter of resignation, addressed to the club's secretary, expresses the memberhs regret at finding it necessary to resign and merely asks that this information be converyed to the club's board.

However, there is another reason for resigning from a club, which must be handled completely differently. Suppose you are resigning in high indignation becuase you have just discovered, as you are organizing your life in preparation for taking public office, that a club to which you have belonged for 20 years is not the affable community of like-minded spirits you had always assumed, but a hotbed of prejudice against blacks, Jews, Roman Catholics, women and people with Hispanic surnames.

You must then make your disillusionment known publicily, so that others will not be similarly decived. It is wise to do so before the matter is brought to your attention publicly by others.

Q: Where does the napkin go at a dinner party -- to the left of the fork, or on the plate?

A: Properly, it goes in the center of the place plate, folded neatly, but not as if you plan to wear it afterwards as a funny hat. If, however, the hosts are serving the meal themselves, and plan to have a cold first course already on the table when the guests are asked to sit down, it is advisable to put the napkin to the left of the forks. A napkin that has been neatly centered in a bed of pate cannot serve its proper function during the meal.

Q: My boyfriend and I are getting ready to celebrate our sixth month going steady anniversary. He's giving me a present. The problem is that I don't know whether I am "supposed" to also give him one. My mother says that it is incorrect for me to because, as a girl, I am not obliged. I feel somewhat awkward since he has already let me know that he has a gift for me. I don't want to seem ill-mannered. Please let me know the proper thing to do. Also, if I should get him a gift? Neither my mother nor I knows what to get him.

A: Would you and your mother please stop thinking along the lines of "as a girl, I am not obliged?" When the Equal Rights Amendment passes, it will be not only ill-mannered, but illegal. However, there really is no such thing as obligatory present-giving. One goes by one's instincts, and yours obviously are to commemorate this momentous occasion.

The general rules about presents between unmarried people is that one gives or accepts only what can suitably be returned during a break-up. (Married couples have the courts to help them decide who gets what after the break-up.) "Take back your mink" is, for example, almost an emotional impossibility, and therefore it would be inadvisable to give your boyfriend a mink coat.

Books, records and small leather goods such as wallets and keycases are considered to be the proper type of present to be exchanged by those in temporary arrangements.

Q: Somewhat enlightened corporations have installed, in dingy surroundings called canteens, machines which dispense somtthing that is passed off for(as) coffee. One procures this liquid by putting coins into a slot. Should one put in more money than required (the current rate is 20 cents) one's change is returned to one (one hopes) through an aperture somewhat below the slot. Recently, Miss Manners, I deposited a quarter in the slot. While waiting for the machine to fill my paper cup, I heard the change cup receive two coins. Putting in my eager fingers, I found that my "change" included the nickel, which I had anticipated, AND a QUARTER! My question, Miss Manners, is this: May I properly (or improperly) keep the unexpected 25 cents? If not, what am I supposed to do with it? Redeposit it for GREAT INVISIBLE COMPANY'S further profits?

A: Miss Manners believes that this form of gambling is prevalent in most states, even in those in which racier forms are illegal. It is therefore Miss Manners' impression that you are ethically entitled to whatever coins come out of the machine, with the understanding that the odds are against you. Miss Manners once enjoued quite a winning streak in an office canteen similar to the one you describe, and was crestfallen when her luck changed and coffee, as the machine claimed it to be, was produced instead of quarters.

Q: Is it polite to include any further explanation, like "We've known each other for 11 months" or "We are waiting for his divorce to become final" or "We live together but we don't share the same bed"?

A: The greatest benefit of civilized society is that respect for others also relieves people of the responsibility for the habits, morals or errors of others.

Thus, a poll taker, friendly-or-other-wise neighbor or Girl Scout cookie has no occasion to approve or disapprove of your living arrangements. Similarly, you have no responsibility for that person's assumptions about you. The explanation that you and Mr. Jones are not married because you are already a bigamist, your grandchildren disapprove, or you don't know each other well enough is superfluous. Explaining your bedding habits to anyone who rings the doorbell is gratuitous, to say the least. If you should encounter this person later, and he says, "But I thought you and Mr. Jones were married," you may then say, "I am afraid you were mistaken," or, if you prefer, "You thought wrong, buddy."

Q: I am always confused when confronted with salad servers. How does one handle the situation?

A: By the handles, of course. Miss Manners assumes that you are talking about the salas spoon and fork accompanying bowls or plates of salad, from which one is supposed to serve oneself a portion.

Using both fork and spoon in one hand, as opposed to taking one in each, is an impressive feat, but of more importance gymnastically than socially. A failure, when salad is involved, is apt to be a dramatic one. Occasionally one sees the fork and spoon joined together scissors-fashion, but that hardly seems of real service to those who have trouble with the one-handed operation, or fair to those who have mastered doing the one-handed trick.

Feeling incorrect? Address your etiquette questions (in black or blue-black ink on white letter paper) to Miss Manners, The Washington Post .