DEAR ABBY: Our married daughter, who lives 300 miles from us, keeps her home spick and span but when she visits us with her family (several times a year), she reverts to her teenage messiness. She never makes a bed, hangs up a towel, cleans a sink or washes a dish.

Her children, ages 3, 5 and 8, always pick up their toys at home, but when they visit Grandma, their toys are everywhere - even when they leave for home. My husband and I love to have them visit, but picking up after them is no small chore.Housework never was one of my favorite things, but I always kept a fairly tidy house and cleaned up after myself. My daughter does that, too, at home, but when she comes to visit, she acts like she's vacationing at a hotel with maid service. Where did I go wrong? - WEARY GRANDMA

DEAR WEARY: You went wrong when your daughter and her brood visited you the first time, and in an effort to make them feel welcome, you picked up after them without suggesting that they make their own beds, keep their bathroom clean and instruct their children to put their toys away. But it's never too late to set her straight.

Parents encourage laziness and carelessness in their children by making no demands on them whatsoever. Children develop backbone and a sense of responsibility when their parents put a little weight on their shoulders.

DEAR ABBY: When my husband and I dine out at a restaurant, we have encountered what we consider a disgusting, offensive practice.

When we are in the middle of our meal, invariably some middle-aged to older man at another table will whip out a handkerchief and vigorously blow his nose, making loud honking noises. Obviously, this does little for our appetite and dining pleasure.

Naturally, we would never bring this to the attention of the offending person, so we thought Dear Abby would relay the following message: "There are at least two people on this planet who regard blowing one's nose at the table grossly ill-mannered." - REPULSED IN FLORIDA

DEAR REPULSED: Make that three.

DEAR ABBY: I recently received your booklet titled "What Every Teen Should Know." I found it to be both interesting and informative, but I was left with an unanswered question. Please don't think I'm stupid - but:

In the section "How to Get Pregnant," you cited the case of a virgin who became pregnant after engaging in heavy petting. Is it possible, then, to transmit the AIDS virus in the same manner? It seems likely to me, but even with all the information presented to students about AIDS, I have never heard this question addressed.

Please hurry your reply. - CURIOUS IN HERMISTON, ORE.

DEAR CURIOUS: According to the Centers for Disease Control, there have been no reports of transmitting the AIDS virus through heavy petting. However, such activity should be avoided with any male partner who is HIV-infected or who is at risk for HIV infection.

What teenagers need to know about sex, drugs, AIDS and getting along with their peers and parents is now in Abby's updated, expanded booklet, "What Every Teen Should Know." To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada), to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)