DEAR ABBY: A couple of mothers in my neighborhood and I teach home preschool for our 2- and 3-year-olds. This month we are talking about conservation. Though these children don't understand all about conservation and ecology, they at least understand the concept that each person can and should do his part to keep our world beautiful and safe.

We would like to do our part by separating our trash into containers labeled "paper," "glass," "aluminum" and "everything else." However, I am confused as to what constitutes recyclable paper products.

Would used paper towels be acceptable or not? What about cardboard boxes -- such as cereal boxes, doughnut boxes, etc.?

Please advise me on any steps I need to take before taking things to the recycling plant. Thank you. -- MAREN IN MESA

DEAR MAREN: Check the Yellow Pages of your telephone directory under "Recycling," "Scrap" or "Solid Waste." You might also contact your local solid waste management office, which is usually a part of the Department of Public Works. Someone there can help you identify local recycling groups, other area schools and groups with recycling programs, local environmental groups, and companies that accept recyclables and process or sell them to reclaimers.

This research will help you find out which materials are being recycled presently in your area, as well as those recycling handlers and processors who could accept the materials you collect.

For further information on recycling, contact the Council for Solid Waste Solutions, 1275 K St. N.W., Suite 400, Washington, D.C. 20005.

Teachers or school administrators who wish to order a free copy of the Council for Solid Waste Solutions manual, "How to Set Up a School Recycling Program," or the "Resource Revolution" video, should call 1-(800)-243-5790.

DEAR ABBY: I used to think mother-in-law jokes were funny. Not any more. I realize that there must be some good mothers-in-law, but I wasn't lucky enough to get one.

My husband's mother refuses to accept that she cannot run my life, and my husband refuses to tell her to quit trying. He says if I have any complaints about his mother, I should tell her -- not him.

He spends a lot of time with his parents, and he does whatever his mother tells him to do. How can I handle this without causing a lot of problems? -- MAD IN MADISON

DEAR MAD: Take your husband's advice. If your mother-in-law tries to tell you what to do, tell her, woman-to-woman, that you are quite capable of making your own decisions. When you involve your husband, you are asking him to fight your battles in opposition to his mother. Not a very good idea. You need a course in assertiveness. (Yes, such courses are available. Check with your local college.)

Another suggestion to improve your marriage: See your clergyperson or a marriage counselor. If your husband refuses to join you for counseling, go alone.

Want your phone to ring? Get Abby's booklet, "How to Be Popular" -- for people of all ages. 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, Popularity Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.

DEAR ABBY: I have a question that has been bothering me a great deal. I feel embarrassed to ask, but I must.

My teen-age daughter has been receiving pen-pal letters from a girl in Ukraine (U.S.S.R.) who happens to live a few hundred miles from the Chernobyl disaster in a city called Dnepropetrovsk. Because I'm a natural worrier, mother of five and pregnant again, every time she receives a letter, I can't help but wonder if it is safe (non-radioactive).

I realize it has been five years since that tragedy, and cleanup has taken place, but I don't know whom to ask. Please help me. -- LOUISIANA WORRIER

DEAR WORRIER: Put your mind at ease. According to William Curtis, project leader at the Environmental Protection Agency's Office of Radiation Programs, there is nothing to worry about. (Mr. Curtis is an oceanographer who journeyed to Chernobyl last year to conduct surveys for the EPA on radiation levels in the Black Sea.) He assured me that if his word isn't enough to ease your worry, you may take the envelopes to be analyzed at any university that has a radiation department.

DEAR ABBY: I know you can help me. I have a son who's 14 years old, and he is terribly afraid of the dentist. I started taking him to the dentist when he was 3 years old, but each time it was a terrible experience.

He has not been to a dentist for a checkup for more than three years because he is terrified of shots. (He even complains about how painful it is to have his teeth cleaned.)

My question is: Are there any dentists in Michigan who treat patients who have a phobia about dentists? My son needs to have a couple of teeth extracted. -- LIVONIA MAMA

DEAR MAMA: If your family dentist cannot (or will not) refer you to a dentist who specializes in phobic patients, get in touch with your county dental association and ask for some referrals.

Please don't cave in on this very important issue, Mama. Proper dental care is essential to your son's general physical health.

DEAR ABBY: "Hurt in Indiana" remarked that whenever she went to her son's home, she noticed pictures of his wife's family prominently displayed all over the house, but not one picture of his family was in evidence. That reminds me of this story:

One of my lifelong friends remarried after her first husband died. Husband No. 2, whose first wife had died, kept a very large portrait of Eve, Wife No. 1, hanging over the fireplace.

Finally, my friend, one of nature's true noblewomen, who wouldn't hurt a flea if she could get out of its way, said to Husband No. 2: "I have a very good portrait of Clifford (Husband No. 1) that would look lovely beside Eve."

The next day Eve's portrait mysteriously disappeared. -- AMUSED IN TULSA

Most teen-agers do not know the facts about drugs, AIDS and how to prevent unwanted pregnancy. It's all in Abby's new, updated, expanded booklet, "What Every Teen Should Know." To order, send a 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, Ill. 61054. (Postage is included.)

DEAR ABBY: For quite a long time now, when certain situations arise, I ask myself, "What would Dear Abby say?" I would like to address this situation:

Before I was married, I visited my parents (they live nearby) several times a week. Now I am married -- with new friends, wanting to spend time with my husband and also visit my other siblings. This means that my husband and I don't visit my parents as much.

The problem? I feel guilty for not spending more time with them. My mother makes comments like, "Oh, we haven't seen you for months!" (Not true, Abby; we see them at least twice a month.)

I know that we are only as guilty as we make ourselves feel, but I would like to know, in Dear Abby's opinion, how often is often enough to visit parents? They don't seem to understand that there are other people in my life now, and working every day makes me tired at the end of the day and weekends are precious. Any comments? -- FEELING GUILTY

DEAR GUILTY: No one can "make" you feel guilty without your permission.

Your reasons for seeing less of your parents now are legitimate, so when you mother "reminds" you that your visits are less frequent, don't apologize (like a child); explain to her -- as you did to me -- that there are other people in your life now, and working every day is very tiring and weekends are precious.

DEAR ABBY: My brother's son is getting married soon in Chicago. The number of family on the groom's side will be limited, as none of us live in Chicago. We will have to fly in the night before in order to attend the wedding, which is scheduled for 2 p.m. We will not be able to leave for home the day of the wedding because there are no evening flights.

So -- after the airfare, hotel for two nights, meals, car rental, etc. -- the wedding will cost each of us well over $700, not including the gift.

I have just found out that the groom's family will not be invited to the rehearsal dinner, even though we are all from out of town. (There will be only six or eight of us.)

We are very hurt to think that we will be left alone in a hotel in a strange city after all of the effort and expense we will go through to attend this wedding.

Don't tell us it is our choice to go or not. We know that, but his wife would never forgive us if we didn't come, and besides, we really want to be there to see this nephew married.

Please try to explain why my brother and his wife are excluding us from the rehearsal dinner. It can't be the cost -- they can well afford a few more dinners. What do the etiquette books say? -- HURT IN NEW YORK

DEAR HURT: I don't know why your brother and his wife are excluding you from the rehearsal dinner if -- as you say -- they can well afford it.

The etiquette books say that all out-of-town guests should be invited to the rehearsal dinner, which is traditionally hosted by the groom or his family.

By popular request, Abby shares more of her favorite prize-winning, easy-to-prepare recipes. To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: More Favorite Recipes by Dear Abby, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)