IT'S THAT TIME OF YEAR AGAIN. Time for pumpkins, cider and witches. Time for things that go bump in the night. Time for my own personal nightmare: How to come up with a classy, clever, inventive Halloween costume or three.

I think there are basically two kinds of mothers: those who have studied with Edith Head and welcome the challenge of creating a stegosaurus costume (complete with plates), and those who schedule major surgery for late October.

From long experience, I suggest the following:

Use what you've got. One year I sent my three out in their pajamas, as Wendy, John and Michael from "Peter Pan."

Spend the last weekend in October at Disneyworld.

Complain so much about having to "build" costumes that the neighborhood seamstress finally offers to make them.

Buy plastic.

When the children are very little, you can get away with a lot more, especially if you don't send them to the school costume parade and contest.

When my older son was 2, I dressed him in Oshkosh overalls, a plaid shirt and a bandanna. We bought a railroad cap and he was an engineer. The next year we lowered the straps on the overalls, added a straw hat, and he was a farmer.

When he was 4 we acquired a hard hat, slung a hammer through the pocket loop and sent him as a construction worker. Unfortunately by then we had moved and the mother now next door had transformed her 4-year-old into a walking, breathing chicken-wire-and-crepe-paper grape popsicle. That was the end of the overalls era.

Last year, at age 6, he wanted to be the Karate Kid. Clinging to two deep-seated beliefs -- that to buy a costume at Toys R Us is a cop-out and that to touch a sewing machine will cause a tension headache -- I searched for white pajamas. It was no go; they're as hard to find as white sheets. In desperation, we enrolled him in six months of classes designed to teach him to "break a brick."

"It would have been cheaper," growled my husband, "to have paid someone to make the costume. We would have had enough money left over to hire someone to break bricks and to send this kid to college."

"It's the principle of the thing," I maintained. "Halloween costumes are supposed to be resourceful."

Of course, no one in my family wants to be a Karate Kid this year. One kid wants to be a Ninja (karate costume dyed black, complemented by cardboard-cutout throwing stars.) One kid wants to be a devil (red material cut to cape shape with stapled-on ties, red construction-paper ears attached to a red ski cap, cardboard trident). One kid, bless her heart, has agreed to be a farmer.

Here are some "resourceful" but easy-to-make costumes. They can even be done by the child with a little help.

PUMPKIN COSTUME --

Paint a grocery bag with orange tempera. When it's dry, cut 5 or 6 inches off the bottom (check the length by putting it over the child's head). Mark spots for eyes, nose and mouth, then take bag off child, draw on jack-o-lantern eyes, nose and mouth and cut them out.

Paint a 3-ounce paper cup brown and glue it to the top center of the bag for a stem. Make a cape out of orange crepe paper, by just pinning it around the shoulders. Brown or black slacks and gloves complete the pumpkin.

EASY WITCH'S COSTUME --

Use a large black plastic trash bag, slit up the side. Tape back one end to form a collar, then pin it in front.

Using black crepe paper, make a tube to fit around the witch's head. Glue the tube closed and let it dry. Then, twist one end to a point, and turn the other end and stretch it outward to form the brim.

Have the witch wear a black turtleneck and a long black skirt, or slacks if she's a witch's-libber.

EASY VAMPIRE'S COSTUME --

See witch's costume cape, but slip a red ribbon under the collar before taping it closed. Tie the ribbon so it shows and wear white gloves.

There are two ways to make fangs. Either cut them out of a well-cleaned plastic dish detergent bottle or (if you prefer to eat your costume at the end of the evening) cut fangs out of a marshmallow.

Slick back your hair with setting gel or mousse.

Makeup: Spread a thin layer of cold cream or hand lotion all over the face. Then pat on cornstarch with a cottonball. Draw outlines around eyes and mouth with dark eyebrow pencil, then color the eyes and mouth with purple or green eyeshadow and paint the lips with lipstick.

Note: Rubber cement makes a great scar. Brush a line of it on a mirror, then put a few drops of red or purple food coloring in it. Let it dry for several minutes, then peel it off and apply it to wherever it will cause the most gasps.

Blood: This can be worn or carried or just made for the "fun" of it. Put a cup of corn syrup into an empty jar. Add a teaspoon of red poster paint then a few drops of yellow and blue poster paint until mixture looks good and bloody.

TRASHY BEHAVIOR --

Use a trash bag again, only this time make legholes in the bottom so the child looks like a walking trash bag. Thread a ribbon through slits around the top, draw it together near the neck after first stuffing it full of child and crumpled newspaper.

EASY CAT --

Keep going on the above costume. For a tail, roll up another trash bag lengthwise into a long, thin tube and attach with tape or staples. For ears, use a dark ski cap and attach triangle shapes made out of black construction paper with staples. Or use a headband and attach ears with tape.

Note: The same ears may be used for a bat with the witch-Dracula cape serving as bat wings.

ROBOT --

You need two grocery store-type cardboard boxes, one just big enough to fit comfortably over the child's head and the other several sizes bigger for the body.

Cut the flaps off the bigger box, but keep those on the smaller ones. Cut a hole in the bottom of the "body box" and eyes, nose and mouth holes in the smaller box. Cover each with silver spray paint or aluminum foil.

Cut the lid off an egg carton and cut the bottom section into six equal parts. Collect jar lids and bottle caps and paint them and the egg-carton pieces with red, yellow and blue poster paint. Decorate the costume with these dials and buttons by gluing them onto the body.

Once the child is in the costume, attach the flaps on the small box to the top of the larger box with duct tape.

Silver or gray tights or slacks and a gray sweatshirt underneath complete the costume.

VERY EASY GHOST --

Drape an old sheet (preferably not a Laura Ashley print) over the child so it reaches just above the tennis shoes. Trim if necessary. Note where the face is and draw eyes with black magic marker. Cut out the eyes inside the marker lines. Draw on a nose and a wicked grin. Armhole slits allow more effective trick-or-treating.