The Great Pumpkin Makes a Great Party Theme : Holidays: Ghoulies, ghosties, long-leggety beasties and things that go bump in the night can all be used to decorate for Halloween.

It’s time to decorate for Halloween, so Beverly Simons is planning a trip with the kids to the you-pick-em pumpkin patch not far from her weekend house near Pawling, N.Y.

“Pumpkins are so cheap, and they make a great decoration,” says Simons, a public relations director in New York City.

She and her husband, Gordon Conley, like to go all-out at Halloween for family and friends. When they give parties, costumes are optional but decorations are a must. Guests sometimes carve and carry home their own jack- o’-lanterns.

At their last party--an indoor-outdoor affair for 35 with carving on the deck--a family of paper ghosts swayed in the breeze in the entryway, and pumpkins consorted with gourds, autumn leaves, Indian corn and bittersweet on tables and mantelpiece. Other times, they bundled corn shucks, 8 feet tall, in ribbons and ringed them with pots of chrysanthemums outdoors.

“It’s not expensive and adds so much to a party when the guests see you’ve gone all out,” Simons says.

Professional party planners, floral designers and interior decorators agree. By combining the bounty of autumn’s harvests with candy corn and candles in traditional colors, they say, decorating for Halloween can be both quick and relatively inexpensive.

Beverly Church, a New Orleans party consultant and co-author of “The Joys of Entertaining” says you should decorate to excess for the best effect. “The entrance sets the tone and, of course, decorate the table where you are serving.”

At the front door, amass pumpkins in various sizes and shapes. You can also pile them in the fireplace--if you’re not planning to use it.

Make a wreath with a base of moss and attach miniature pumpkins, fresh flowers and autumn leaves.

Bales of hay can be used for extra party seats. For added decor, tie the bales with big ribbons, plaid perhaps. To make cleanup easier, carry each bale indoors in a large plastic garbage bag. Once the bale is in place, roll the bag down and tuck it underneath. Before removing the bale, pull the bag up to cover.

If you’re using place cards for dinner, Church suggests: Write names in silver on autumn leaves. Slit miniature pumpkins across the top and insert a leaf in each. Silver (and gold) marking pens are available at art supply stores.

For easy entertaining, Church combines the menu with the decor. She orders a 6-foot hero sandwich with fillings only in the four feet in the middle. She then uses each end of the bread for a floral arrangement. From the top of the loaf she scoops out enough bread to insert a small bouquet set in a plastic bowl and florist’s foam.

New York decorator Sam Botero likes to take the familiar elements of Halloween and use them in a slightly different way. For example, cut a big jack o’lantern out of orange paper and use the cutout as a base for a table arrangement of gourds, candy corn and black and orange tapers.

Another idea for a table: Arrange corn husks radiating in a circle from the center of the table. Fill small clear glass bowls with candy corn and intersperse them on the husks with orange and black votive candles and tiny gourds.

For a more sophisticated look, steer clear of the true black and orange colors.

“Soften them by using natural tones in an orange cast,” says Renny Reynolds, a floral designer whose book, “The Art of The Party,” will be published by Viking Penguin next year. “Hydrangeas and pyracantha, which has bright orange-red berries, can be cut from the yard. And peach-tone flowers like roses go beautifully with these.”

Even if you’re a sophisticate, you don’t have to forgo fantasy. Reynolds dresses old mannequin parts and arranges them on a table as if the rest of the figure were under it.

“There are wonderful inflatables around now,” he says. “Dinosaurs and pterodactyls are available and more interesting than the obvious Mylar balloons. Look for them at a natural history museum or toy store.”

“The phrase that identifies Halloween is ‘trick or treat,’ ” says R. Scott Bromley, a New York architect who often decorates night clubs. “Make the decor so bizarre that people know you are tricking them, and it will be a treat.”

For a table centerpiece, he suggests creating illusions like an upside down fruit compote using wax or wooden fruit, glue and skewers.

“Turn your pictures upside down,” he says. “If you’re serving dinner, use mismatched cutlery and plates.”

In dance clubs, lighting and reflective surfaces are used to create mysterious spaces, and Bromley was a master of the big effect in his decoration of New York’s Studio 54 in its prime. He says you can change the dimensions of a room by tacking up mosquito netting or creating a forest of “trees” from slim strips of Mylar that run ceiling to floor.

“Once,” he recalls, “we filled a vestibule halfway up with plastic packing pellets and people had to walk through the pellets to get to the party.”