Q. In September, our 20th high school reunion is planned. What does one wear? It's a buffet dinner with dancing.

A. Keep in mind the purpose of a high school reunion, which is to give those who would least have suspected it the impression that you turned out to be a success in life, after all. (If you were elected Most Popular Boy or Girl 20 years ago, you still have to show that you were able to translate your early triumphs into modern, adult terms.)

Therefore, you dress to look as rich and chic and attractive as possible.

A word of caution, however. The nature of a reunion recreates attitudes of the original time. You will suddenly find yourself and others thinking in cliches you may not have used for years. If you overdo your act, it will be recognized with adolescent cruelty that you are a "show off," "boy chaser," person who "thinks he's so hot," or whatever.

So summon up whatever subtlety and finese you may have acquired over the last two decades -- and then fix yourself up to kill. Surely you remember how hard you tried to look as if you didn't care whether anyone liked you or not in high school; now you ought to be able to bring that off.

Dark, banker's suit for men; plain dress with one small piece of good jewelry for women. Good tailoring and a 1980s hairstyle for grownups (rather than a 1960 teen-aged look) are essential.

Q. Our son is planning to ask a girl from another city, a distance of 400 miles, to marry him. If they become engaged, what are our responsibilities? We have met his girlfriend, but have never met her parents. Do we a) call them and invite them to visit us? b) call first and then visit them? c) wait for them to call us?

Any visits must be overnight stays because of the distance. Our home is adequate for our family; however, we have three other children at home and cannot offer house guests a private bath and other conveniences conducive to privacy. If they come to visit, would it be proper to accommodate them in a nearby hotel? If yes, should we pay the bill? Also, if we visit them; should we expect to stay with them or arrange our own accommodations?

A. If you choose c), you may wait forever. Society has changed since the rule about the parents of engaged couples was invented, and no one has bothered to revise it to meet such outrageous situations as engagement between couples whose parents live 400 miles apart. This has resulted in a great deal of confusion-and hurt feelings that are better saved for the wedding.

Miss Manners will now come to the rescue.

Here is the old rule: The young man's parents call on the young woman's parents. ("Calling" referred to the now-defunct custom of arriving at their doorstep for a short surprise visit that would not inconvenience them because everybody was always calling on everyone else all the time, and therefore it was no surprise at all.)

Here is a new rule: The young man's parents initiate the relationship by telephoning or writing the young woman's parents and expressing their desire of becoming acquainted. The details of the meeting are then worked out with the help of two people who are in a position to know what would be most convenient for each household -- the young couple.

All you have to do, then, is to call or write the other parents and say, "We're so pleased. Dorabelle is such a lovely girl. We're anxious to meet you, and would love to have the pleasure of entertaining you here."

Assuming that Dorabelle has warned them about your limited bathroom facilities, they can accept or counter-invite you to their hometown. In either case, saying "I'm afaid we don't have room to make you comfortable, so I've made a hotel reservation for you nearby" is proper. Paying the hotel bill of your guests is charming if you can easily afford it, but if not, don't worry about it.