DEAR ABBY: I have a suggestion for your readers. Tell them to urge their parents to identify the photos of their ancestors. When our parents died, my sister and I had no idea who was in the photographs we were left.

Fortunately, my sister traveled to Denmark and was able to get in touch with relatives who could identify the people. -- MARILYN BIRD, ROSE CITY, MICH.

DEAR MARILYN: I couldn't agree more. A few years ago, I received this letter that dealt with the problem:

DEAR ABBY: You suggested that "older people" should mark the backs of family pictures while they can still remember who's who, when the pictures were taken and the approximate dates. Why only "older people"? That's something everybody should do as soon as a snapshot is developed.

For years, I was too busy (or too lazy) to do it, and now that I'm retired and have plenty of time, I can't remember who half the people are.

My parents can't help me because my father has been dead for 25 years, and my mother is in a rest home, unable to remember much of anything.

So here I sit, with a big box of family pictures -- beating my brains out trying to recall names, dates and places. What a mess!

Abby, please remind your readers often to label their pictures. Then their grandchildren won't have to go through what I'm going through now. -- KICKING MYSELF IN ASBURY PARK

DEAR KICKING: Not only should family pictures be labeled, but accounts of historical events and newspaper clippings of births, graduations, marriages and deaths in the family should be preserved in a sturdy scrapbook.

Fascinating family histories could be preserved if younger members interviewed older relatives at family gatherings. A tape recorder would be ideal for this purpose.

Succeeding generations will love it!

DEAR ABBY: My husband and I disagee on how our children should address their elders. My husband and his family feel that children should always address adults as "Mr. or Mrs. So and So," regardless of the adult's preference -- otherwise the child will not learn to respect adults.

What is your opinion? Should my children address you as "Miss Van Buren" even though you ask them to call you "Dear Abby"? -- PREFERS FIRST NAME

DEAR PREFERS: To show respect to an adult, one addresses that person as he/she asks to be addressed.

If a man named "Rudolph" says, "Please call me Rudy," to ignore his request and call him "Rudolph" would be rude.

DEAR ABBY: Regarding thank-you notes: I believe I received the tackiest thank-you note ever -- my canceled check with "thank you" written in the "memo" space. -- APPALLED IN SODUS, N.Y.

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.)

DEAR ABBY: I've been reading your column since I was a pre-teen girl. I'm 21 and a college senior now. In my freshman year, I met a super guy, "Ray." We hit it off immediately and have been best friends ever since. Abby, Ray was my first love. There was a strong physical attraction between us (we even discussed it), but we didn't act on it for fear of jeopardizing our precious friendship.

Since we met four years ago, I've dated others, lived with someone else, and now Ray has a girlfriend. She is his first serious relationship. Now I am wondering if I should let him know that I am still in love with him. We still are very close friends, and I honestly believe that we could make it as a couple.

I don't expect him to drop his girlfriend for me. However, I cannot spend the rest of my life wondering what might have been had I been willing to risk telling him my feelings.

What do you say, Abby? -- "WHAT IF" IN SACRAMENTO

DEAR WHAT IF: Now that Ray is involved in his first serious relationship, were you to tell him that you are still in love with him, it would cause him no end of consternation. Please, give him a break and put your "true confessions" on hold until you know where Ray's present relationship is going. Should it not endure, and he is free to consider another love relationship, unleash your "confession." But not until.

DEAR ABBY: I am stumped as to what to do about something that happened at work. As a junior executive in a large firm, I submitted an idea to a vice president. He reacted with very little enthusiasm, so I assumed he didn't think much of my suggestion.

About a week later, he showed my idea to the president of the company as though he had originated it. The president thought it was brilliant.

I was furious when I heard what had happened and I wanted to tell my friend a thing or two. However, I took a co-worker's advice to just keep quiet, as any further action on my part could be harmful to my career.

I am still very resentful, seeing his career flourish and not my own. Any advice? -- HAD IT WITH OFFICE POLITICS

DEAR HAD IT: I think you used good judgment in taking your co-worker's advice. Let it go -- and learn from the experience. And the next time you get a "brilliant" idea, submit it to the president yourself.

DEAR ABBY: My husband and I just returned from the beach -- our first outing this season. It was a beautiful sunny day in Santa Monica, and the beaches were swarming with men, women and children. I had seen some ads of the new skimpy bikini bathing suits for women, but this is the first time I had seen them worn by real people.

Abby, from behind, some of those women appeared to be naked -- with just a wee little string back there, barely visible, attached to a small patch of fabric in the front, no bigger than a Band-Aid.

I am not some crotchety old woman; I'm 35 years old, but I must admit, seeing so much flesh exposed, I didn't know whether to laugh or cry. (My husband laughed.) -- EUGENIA

Most teen-agers do not know the facts about drugs, AIDS, and how to prevent unwanted pregnancy. It's all in Abby's 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: We are a middle-class family with a 20-year-old son and a 16-year-old daughter. Our problem is the girl -- "Karen." She's been going with the same boy, "Mark," for a year and a half. He's 17, and they are so wrapped up in each other, it's terrible.

Karen was always a happy, outgoing girl, but now she's secretive and quiet. She used to confide in me. She doesn't go places with her girlfriends like she used to; they don't even call her anymore. Her grades have plunged this year, so she has to go to summer school to make up some credits.

I have tried to reason with her. We have restricted her to seeing Mark only once a week because they were getting too thick. (She says she "loves" him.) We have talked until we are blue in the face about doing something besides waiting for Mark to call, but she can't -- or won't -- see the light. What can we do? -- KAREN'S PARENTS

DEAR PARENTS: Your daughter has a bad case of lovesickness. She needs someone she can talk to honestly about her feelings. Unfortunately, there is now little communication between you and Karen. So, family counseling might bring you closer together.

Karen needs to see you as loving parents, which is what you are, instead of "the enemy" -- using your parental power to keep her from seeing the boy she loves. (Don't ridicule her; although she is only 16, her love is genuine.)

Ask your family doctor to recommend a family therapist. If money is tight, your YWCA may be the answer. And hats off to you for seeking help.

DEAR ABBY: I need your opinion. Two weeks ago, I gave my girlfriend an engagement ring. We have been going together for nearly two years, and it's understood that we will get married in about a year, so she wasn't exactly surprised. (I am 24 and she is 21.)

Now, the problem: The ring I gave her is a three-carat zircon -- set in white gold. It looks exactly like a diamond, but it is not nearly as expensive. I never did tell her it wasn't a diamond, and she has been showing it off at work and to her relatives. Now I'm too embarrassed to tell her the truth.

I keep thinking that one day, when I can afford it, I will replace it with a real diamond, but now I don't have the nerve to tell her the truth. What should I do? -- NO GUTS

DEAR NO GUTS: Please get the guts to tell her the truth, and the sooner the better. If she should decide to insure the ring, she would be told immediately that it is not a diamond. Your engagement would be less "rocky" if she heard it first from you.

DEAR ABBY: My mother-in-law's behavior is sometimes very puzzling to me. She will bake (or buy) some sort of pastry or dessert to take with her when invited to a get-together for a special occasion. (Birthday, anniversary, housewarming, etc.)

When the get-together is over, she always goes to the kitchen and packs up whatever is left over from her "offering" and takes it home with her. Trying to get her to leave even a portion of it is like pulling teeth!

I'm embarrassed when she does this in front of my family, or even her own children. My husband and I feel that whatever she brings to the home of another is a gift, and she has no right to take home even a part of it. -- CONFUSED IN MARIPOSA, CALIF.

DEAR CONFUSED: The leftovers should be left -- unless, of course, the host or hostess insists that the donor take them home. And by the way, when one takes a "goody" to the home of another, it would be very thoughtful to bring it on a paper plate, a box, or some other type of disposable container that need not be returned.

Abby's family recipes are included in her cookbooklet. Send a long, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Cookbooklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)