DEAR ABBY: What can you do when you have a sloppy, inconsiderate roommate? I've been living with the same girl for a year and a half now and have kept hoping things would improve, but they haven't.

I'm not saying I am the world's best housekeeper, but for some reason, my roommate thinks I am the maid. We both agreed to share the responsibilities like taking out the trash and doing the dishes, but if her set of dishes sits there for five days, I'll do them. That's where the problem is - she knows if she lets something go long enough, I'll do it.There are towels on the bathroom floor, blankets and pillows left on the living room floor, and peanut butter and jelly jars left open on the kitchen counter. I can't help feeling that she's taking advantage of me.

How can I let her know she's being a total pig without hurting her feelings? - NOT HER MAID IN ALTOONA, PA.

DEAR NOT: The key to your problem is right in the middle of your letter: "She knows if she lets something go long enough, I'll do it."'

Don't permit her to let something go; when it's her turn to do it, point it out, and keep pointing it out until she does it. And insist that she do it before she goes to sleep. Be firm.

You may have to remind her five or six times - but keep after her. And if you permit her to procrastinate, she may be a total pig, but you're a jellyfish.

DEAR ABBY: My daughter has saddled me with an enormous job - writing names on the backs of pictures, or under them, in many, many albums. Over the years, no one thought to do this.

We have a cedar chest and several shoe boxes filled with snapshots. Some I inherited from my mother, and none of hers had names on them.

Abby, please tell your readers to start identifying pictures for posterity. Their progeny will surely appreciate it. There are many pictures of people I cannot name. - MRS. O.H. DODD, RAYMOND, WASH.

DEAR MRS. DODD: You must be a new reader. Read on:

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 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, uanble 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 clipping of births, graduations, marriages and deaths in your family should be dated and kept 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!

"How to Write Letters for All Occasions" provides sample letters of congratulations, thank-yous, condolences, resumes and business letters - even how to write a love letter! It also includes how to properly address clergymen, government officials, dignitaries, widows and others. To order, send your name and address, plus check or money order for $2.89 ($3.39 in Canada) to: Abby's Letter Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)