WHEN Washingtonians say "The White House belongs to all The People," they mean that they feel entitled to be invited to dinner there, whether or not they have shown any kind feelings for the host.

The value of such invitations, among those who occasionally receive them, is not in the expectation of seeing magnificent clothes and jewels or hearing the political secrets and sparkling conversation of the country's most intersting citizens. White tie and ball dresses with 18-button white gloves haven't been worn there in years, the people you are likely to meet are distinguished by the size of their political contributions, and what they are busy doing is stealing souvenir matchbooks and menu cards andd looking to see who is famous. The only state secret you will hear is that the president feels a deep and personal friendship for whomever happens to be that week's guest of honor. (This perhaps unpleasant, but not unpatriotic, cynicism on Miss Manner's part is at least nonpartisan. She has been watching the scramble for White House matchbooks for the last six administrations.)

The value of the invitation is that one can cancel one's previous engagement by saying, "I'm afraid I must go to the White House that night." If necessary, one must make a previous engagement hastily for the purpose of doing this.

Here are some other things you need to know about attending a White House dinner, but other advisers are afraid to tell you for fear of sounding disrespectful:

It is not true that only extreme illness or death prevents otherwise well-bred citizens from accepting a White House invitation. Any important event or geographical distance is considered a sufficient excuse. What is rude, however, is to refuse and then to brag that it was really disapproval of the president's stand on some issue that motivated you. This only points out that you didn't take this stand publicly before, or the president would not have invited you.

Dress as you would for a dance at a conservative country club: black tie and nonadventurous long dress. Anything unusually magnificient or chic will make you look as if you are trying too hard to be noticed.

You needn't rent a limousine if you don't happen to have one lying around the garage. Many people drive their own cars, and parking space is provided on the Ellipse.

Don't forget the enclosed admittance card, which will be tested by machine to see if it is a forgery. Of course your face is your passport -- until you try to travel on it.

You will be told by an aide that husbands should precede wives in the receiving line. Only if they are the reason for the couple's being invited. If the wife is the office holder, she should go first.

However much the president and his wife express delight at seeing you, they are not eager to talk to you during the receiving line. Say "good evening" and move on.

Don't worry about minor points of etiquette, because the staff (many of whom have been hired for the night) and social aides are accustomed to stirring people through. If a social aide asks you to dance after dinner, however, it is not because you are popular.

It is not only gauche, but useless to try to have a substantive conversation with someone you might not otherwise meet. Anyone that much more important than you will relentlessly return penetrating questions with comments on the weather, dinner and entertainment.

It is not true that no one may leave before the president retires. Many a president who loves to dance all night has been left there -- first by crochety Supreme Court justices, then by a tolerant first lady and finally everyone else except the three least important women at the dinner.

If your invitation is for 10 o'clock, eat a good dinner secretly in your kitchen. You have been invited as a secondary guest, to the after-dinner entertainment only. But you needn't mention that detail when describing to friends later what a glittering and glamorous dinner it was. MISS MANNERS RESPONDS

Q. My son and his wife were visiting for a week with their children. Whenever the phone rang, one of them always seemed to answer for me.. If the caller had asked for me, they would always question, "who shall I say is calling?" I take this as an invasion of my privacy. I do not feel it necessary to be identified over the phone except at a place of business. When a caller asks to speak with "Mary," then Mary should be summoned to the phone. As I have said nothing to them, I am hoping you can clarify the subject in your column, and perhaps, somehow, I can leave it near the telephone for perusal.

A. Miss Manners refused to speculate about whether your relatives are being nosy, helpful or both. But people's telephone preferences vary so much that she sees nothing wrong with your saying politely, "It isn't necessary to screen my calls for me. I'll talk to whoever telephones." If this were a better world, where only one's friends called one at home, Miss Manners would recommend this policy to everyone.

Q. I have acquaintances who seem to remember the teaching that crusts or other "pushers" to assist food onto a fork are taboo beyond the nursery table. Their solution is to use one or more fingers for the purpose, with fingers busy in their plates throughout a meal.

This could be something which has developed from the proliferation of dips and fast foods, but I find it somewhat distressing to see. Would you please say whether I am just slow in moving with the times, or whether I may be permitted to shudder?

A. Yecch. Distressing it certainly must be, to see all your friends with their busy fingers in their plates, but when they claim to be doing this in the sacred name of manners, bragging that they are not using bread for the purpose -- well, that is truly disgusting.

Using bread to sop up sauces is a middle-European custom of dubious class origins. The way to do it, if you must do it at all, is to put a small piece of bread on the plate, spear it with the fork as if it were a food ligitimately domiciled in the dinner plate, and then quickly mop it up.

It is Miss Manners' belief decent-minded Americans, with pure minds and bodies, are perfectly capable of triumphing over any article of food without calling in assistance from the breadbasket. Chasing down the last pea, and capturing it with only a fork as a weapon, is an exhilarating sport.

Sopping up sauces with bread should be confined to the nursery -- "nursery," in this sense, meaning the family, of whatever age, at home enjoying garlic butter in privacy. Using the fingers should be confined to oblivion.