GRADUATIONS ARE the perfect preparation for that laughable institution known on such occasions as Real Life or The World Out There. If you can sit quietly in the sun for two hours, listening to irrevelant platitudes with a respectful look on your face, and can survive with dignity the social mixture of your origins with your peers, life out there should hold no further terrors.

It is a mistake to think that graduations are held for the benefit of graduates, who therefore should be able to enjoy the celebrations as they choose or even boycott them. Graduations are held to mark the end of the sufferings of people who have been paying staggering tuition bills, nagging about homework until their own lives have no longer been worth living, or despairing that the efforts of their ancestors to achieve a modicum a civilization have been lost under their supervision.

The relief of these people on finding that one of society's most obvious goals has been achieved often borders on the hysterical. Otherwise sensible and reserved parents will attempt to involve their graduating children in odd forms of exhibitionist behavior, and encourage younger siblings to do the same. fThey will create havoc by taking pictures at every possible moment, and when they are unable to accost strangers to find outlets for bragging, they will encourage such remarks with each other in unnaturally loud voices.

All this must be endured with grace by indulgent graduates. Not looking ashamed of one's parents, no matter where they demand to be shown, whom they insist on meeting and what they cannot be prevented from saying, is a rite de passage certifying the maturity of the graduate.

He or she is not, however, permitted any unconventional behavior. Blue jeans that can be seen below academic robes, protest demonstrations against the school or any of its invited speakers, or any behavior -- other than accepting prizes -- that distinguishes one graduate from another cannot be tolerated. The graduation ceremony, in all its mesmerizing monotony, was carefully designed to fulfill the fantasies of families, not to enable the graduate to express his independence.

Even the allegedly private aspects, the proms and the parties, carry their family obligations. If you pose prettily beforehand, and fabricate a comforting report afterwards, it is possible that you and your peers will be allowed a small amount of private pleasure in between.

Satisfying one's family by going along with all their graduation expectations, no matter how silly or embarrassing, is not the graduate's only obligation. He or she also owes something to the school's older alumni -- or if not, it isn't from the lack of trying.

Alumni who are using graduations as the setting for their reunions are not always raucous and drunk. However, they are always caught in a mysterious time warp that leads to behavior that can be just as offensive.

Graduating seniors must listen with patient smiles to the questions and comments of alumni who have discovered that the school no longer has curfews, single-sex dormitories or four years of required biblical studies. That look will serve them well on job interviews and other such exasperating situations held Out There. MISS MANNERS RESPONDS

Q. Help! My wedding invitations just came and they look beautiful, but I have some questions about how to send them and I get different answers from different people. You've got to help me before I go crazy. It's only two months before the wedding. Do I throw away the tissues that come with the invitations, or do I leave them? Do I stuff the inner envelopes with the folded part on top, or the open part? Should I put stamps on the little envelopes that go with the response cards?

A. You are hysterical. Please get a grip on yourself. How do you expect to cope with marriage, and perhaps a family, when a few tissues and envelopes can drive you off the deep end?

The folded side of the invitation goes deepest into the envelope. The tissues are intended to prevent the engraving from smearing. Most people leave them in, but, then, most people cover the arms of their sofas with extra sleeves, too. Miss Manners prefers to take her chances with the ravages of life.

You will be alarmed to hear that there is no rule about stamping the envelopes of response cards because there is no rule that allows response cards for a wedding invitation to exist at all. The custom is of recent and, to Miss Manners' finicky mind, dubious origin. So you are on your own about the stamps. If you find yourself incapable of making such a decision, let Miss Manners know and she will dictate to you the exact, correct form of canceling a wedding.

Q. I am a single woman who hates to cook and lives to eat. For years, I have coaxed people from the office to go to restaurants with me, bought carryout food, treated people I didn't really like -- all because I was embarrassed to eat in a restaurant alone.

Now I've had enough of that. I've always been liberated enough to support myself -- never had a good enough offer to do it for me -- so I ought to be liberated enough to go out by myself. Do you have any hints on how a woman can manage by herself? Should I take a book, for instance? (I love to read almost as much as I love to eat, but I don't like to do the two together.)

Someone suggested taking a briefcase, so I look like a traveling businesswoman, not a potential pickup. Do I have to stare out in space, pretending to see nothing? I would really prefer to look around -- it is one of my hobbies to make up stories about the lives of people I glimpse in public -- but I have heard that women alone are generally seated out of the way. What I need to know is how to be inconspicuous, so I can enjoy myself without being bothered.

A. There is nothing so conspicuous as a woman struggling alone in a public place with the effort to appear inconspicuous. Such a performance positively inspires harassment of all kinds.

A conspicuous woman, in contrast, inspires respect. Miss Manners is not talking about vulgar behavior, of course, but about the sort of aura that surrounds someone who not only has an obvious right to be there, but probably owns the corporation that owns the restaurant. Asked to be seated where you prefer, and behave as you nornally do -- good restaurant manners are no different for single women than for anyone else.

The only prop Miss Manners uses for solo appearances is a head held high, although she has been known to render it more conspicuous by placing a hat on top of it.