Q. "I have an 18-month-old, as well as children who are 7 and 11, so it's been a while since I've dealt with a toddler and there's much I've forgotten.

"My main concern at the moment is how to get some housework done while still giving my little one attention and stimulation. I didn't do that well with the first two, so I need help. Let me say that I erred on the side of the kids rather than the house the last time. They were the center of all my time, as well as my excuse for not getting anything done. I often resented them for their total occupation of my time, and I came to feel really bad about the more-than-just-messy environment in which I was rearing them.

"This time I am determined to be a better homemaker, but I don't want to do it at this child's expense. Nor do I want, nor can I afford, much outside care for him. I will trade babies with one friend every other week or so, but this sometimes seems to take more time and energy than it's worth.

"I need suggestions for learning how to keep house and keep order with the baby in tow.

"Some people manage. Why can't I?"

A. We can understand your concern, but the parent who errs on the side of young kids is hardly in error. A child is much more important than a house, and for that matter, so is a mother. Once you recognize that both of you have rights, there will be little resentment.

There are certain inevitable results that children create and these must be recognized too.

Any room in which a young child plays is going to be rather messy most of the time, but when the whole house gets too messy too often you're seeing the result of the resentment, rather than the cause of it. The relentlessness of motherhood can be so overwhelming it seems impossible to do all that is expected, and so you let everything pile up as if to say, "Hey, appreciate me! I'm such a good mom I can't possibly have time to clean house."

Most of us have gone down this route, especially with the first or second child, but we're sure that won't happen to you this time because you won't need so much reassurance; because you know enough to make some time for yourself; because the third child makes a parent much more efficient; because you truly want to be neater, and because you know what's necessary and what isn't.

There are some practical measures you can take:

Let your child keep some playthings in a drawer, a box or a shelf in every room in which he's welcome -- even your bedroom if he plays there. He can have a special cupboard of your pots and pans in the kitchen and a net sack of his rubber toys in the bathroom, but there should be some books in the living room; a few stuffed animals in your bedroom. This often stops a small child from dragging so much out of his room every day.

Buy toys with only a few pieces, and don't get huge ones like a rocking horse or a slide unless you can keep them in the basement or garage. If they dominate the living room you would feel taken over by your child -- and resentful.

Restrict big-wheeled toys and balls to the yard or the basement. They invite trouble inside.

Keep your treasures on high shelves so you won't be anxious about them.

Do your cleaning and laundry in the morning (or not at all). The rest of the day is spent enjoying your child, keeping up with the mess and fixing lunch and dinner. You wouldn't work full blast in an office all day, and you shouldn't do it at home either.

Rinse a diaper as soon as it's changed and put it in its pail. Wet diapers on the floor or in the john are simply depressing and always embarrassing if someone visits.

Expect to leave a room as clean as you found it, swooping up the pots and pans with at least a pretense of help from your child, and say you have to do it before you can take a walk or read a story. This lets you keep up with the debris.

Sweep everything in the middle of the floor -- if the room is too chaotic -- and throw it in a basket, to be sorted when there is more time.

Yell "Blitz" and set the timer to ring 15 minutes before you expect someone -- including your husband -- to walk in the front door. You and your children pick up all that you can before the bell rings, and then ignore the rest.Children will try harder if they know the job will end soon -- and so will you.

Let your baby have a good soak in the tub every day, and if you have two bathrooms, alternate their use. This gives you time to straighten the medicine chest, scrub the tiles and clean the fixtures. Never will this room be so tidy again.

Play with your child while he's still content, rather than waiting until he cries, for it takes twice as long to placate him then. It's easier to get your work done if your child is happy.

That's one reason why we think your child should spend a lot more time with other children. He thrives on company.

It's true that two children can make twice the mess, but if you don't want other children to visit much, you can join (or set up) a baby-sitting cooperative so he can be sat at someone else's house a couple of times a week. A child learns so much when he plays with friends.

You also can keep him busy at home by trying the dandy suggestions in the 3-volume Nova University "Play and Learn Series" by Don Adcock and Marilyn Segal (Oak Tree Press, $3.95, $4.95 and $5.95), which has a book for every year between birth and 3. The pictures are terrific, and so are the ideas.

Your child will still make a mess but at least you'll know he's learning.