HOW MUCH time and care you put into selecting a wedding ring will depend, of course, on how long you plan to wear it.

Rings are terribly important, as every 18-year-old beauty knows. Back in Miss Manners' day, when pre-marital break-ups were all the rage (but some of the current fashions in gender relations were not quite so popular), many a young lady first truly understood the enormity of fate's ironic cruelty when confronted with a valuable ring, a worthless man and the impossibility of keeping one without the other.

For all the changes in the society since, wedding rings, Miss Manners has noticed, still carry great emotional weight. She has noticed, for example, the vestigal digital habits of ladies who steadfastly are refusing to marry the gentlemen with whom they cohabit, or who have discovered that, contrary to the promises of bridal literature, it was their divorce days that turned out to be the happiest occasions of their lives.

These ladies have nevertheless popularized an ornament that Miss Manners calls the "Ms. Ring." This consists of an odd-shaped ring, usually without stones, worn on the third finger of the left hand. It is by no means a conventional wedding ring, but it could be a hand-crafted or otherwise "original" one. Sometimes, a ring is also worn on the right ring finger, as if in explanation that the left hand was only used when all others were used up.

It is not that these ladies wish to be ambiguous about their marital status--often the contrary is true. But, Miss Manners believes (outrageously over-analyzing motivation for wearing of jewelry, which is, after all, a natural instinct) they still cling to the symbolism while rejecting the act symbolized.

Another such instance is the anxiety of widowed and divorced women about their leftover symbols. One would think that the decision about rings would be based on the rather blatant but practical symbolism of indicating whether or not the lady wishes to receive suitors. Yet divorcees who are fond of their rings but feel they ought to want to fling them into the ocean, and even sentimental widows, whose friends enjoy torturing them by telling them they are no longer "entitled" to wear their rings, feel uncomfortable about making their own choices.

Happily married people, especially ladies, who don't like to wear rings, or who don't like always to wear the same one, are subjected to ominous accusations. Others make ridiculous efforts to avoid disturbing the symbolism--Miss Manners once knew a lady who refused to have her ring cut off her infected and swollen finger because she had "never once had it off in nearly 40 years of marriage." She had actually had the finger on for longer, but preferred the risk of losing it to the certainty of violating a symbol.

All this strikes Miss Manners as extreme confusion of a symbol with the thing symbolized. The wedding ring is an old and charming custom, but the permanent wearing of it is not. A hundred years ago, nothing by Miss Manners' calendar, it was not uncommon for contented wives to nevertheless give their rings to their sons for their brides. The engagement ring is a newer and less charming custom, intended to represent down payment on the bride. Far be it from Miss Manners to object to beautiful rings, romantically presented, but anyone who believes that there is no "real" betrothal without a ring, perhaps specifically a diamond ring, is headed for more than symbolic trouble.

So go ahead, little bridal couples, and choose your lovely rings with aesthetic, financial and practical care. (A lady who has a diamond wedding ring, for instance, will probably want a plain gold one as well that doesn't ruin her stockings daily or clash with her jogging outfit.) Enjoy them as long as the symbol and the symbolized go happily together ever after. But if you find yourself dissatisfied with one, you need not necessarily divorce them both. MISS MANNERS RESPONDS

Q. My niece and I are arguing about how to address friends of my family:

A former neighbor of hers, a lady schoolteacher, permitted her to call her by her first name when she reached her 18th birthday. Now she allows herself to address all the people she gets in contact with by their first names, which embarrasses me. Would you please comment on this argument?

A. You are going to have a hard time believing this, and Miss Manners has a hard time saying it, but we live in a world where there are people who are insulted by not being called by their first names, right along with people who are insulted by being called by their first names. The former often say it makes them feel old, as if there were anything wrong with that. If you want your niece to be polite in such a chaotic world, you need only encourage her to inquire of individuals their preferences, and to follow those preferences.

Q. Let me describe this situation for you. I'm invited with my family to a friend's house. I'm seated next to the hostess. After a few minutes of eating, I find about two or three pieces of hair in the food. The hostess, it looks like, sees them, too. What do I do?

A. You have no idea how glad Miss Manners is that the letter is from the guest in this situation, rather than the hostess. Your conduct is simple. You have no choice but to ignore your discovery. You may also feel compelled to ignore the rest of the food, in which case Miss Manners asks only that you do so inconspicuously, as if you had simply had enough to eat.

The hostess has a choice between expressing horror and apologies, in which case she must immediately remove the food and bring you something else to eat; or ignoring the situation, too. If she does not have a substitute meal ready, she is likely to choose the latter. You may be sure, then, that the rest of her meal till be worse, or hairier as we say, than yours.

Q. Recently I mailed a letter to a person who is my child's custodial parent and my divorced spouse. My communication with this person has been strained since the first legal action, which was several years ago. Few such efforts have been effective, and none have been cordial, although brief.

On this occasion, my letter regarded rather simple but important matters concerning visitation. The last address available to me was a business address for this person, which I used. Also, I mailed my letter certified, return receipt requested.

I have not received a proper response to my letter, but I did receive a brief telephone call. During the call, I asked for answers to the question in the letter, to which the response was that no answers were deserved, because the letter had not been presented well. (I presume this to mean, by certified mail. By the way, the receipt was signed by a supervisor.)

My question to you, Miss Manners, results from that comment. Is it proper to use certified or other special mail when the letter concerns non-commercial matters? Also, was my decision to use certified mail in this case, despite the unintended involvement of a supervisor, a breach of etiquette?

A. Miss Manners hopes that it will not come as too much of a shock to you if she informs you that you do not have a truly cordial and happy social relationship with this person. Perhaps you have even noticed this yourself, in the course of your various dealings with each other.

What you may not know is that people who do not get along often employ etiquette as a weapon, claiming rudeness in the other person as an excuse for their dislike. If necessary, they invent rules, which they then declare have been violated. Is there a rule of etiquette that sending non-commercial letters by certified mail is an affront to social decency? Don't be silly.