The Audubon Naturalist Society presents a decoy- demonstration this Saturday and Sunday in Chevy Chase. Seven award-winning artists will display their work and discuss techniques of carving. There'll also be two guided nature walks each day.

Or you might like to tune into the Washington Ringing Society and the National Park Service's bell-ringing demonstration Saturday morning in the tower at the Old Post Office in Washington.

Admission to the following activities is free unless otherwise noted.

ANTIQUE SHOW AND SALE -- Friday, 11 to 8; Saturday, 11 to 6, St. Ambrose Church, 3901 Woodburn Rd., Annandale. A benefit sponsored by the Fairfax County Medical Society Auxiliary. 620-3604.

HOLIDAY BOUTIQUE -- Friday, noon to 8; Saturday, 10 to 4, Tower House, Lucia Lane, Mount Vernon (off George Washington Parkway south behind Cedar Knoll Restaurant). 35 craftsmen display their work. 360-3553 and 780 9806.

SUGARLOAF AUTUMN CRAFT FESTIVAL -- Friday, noon to 6; Saturday, 10 to 9; Sunday, 10 to 6, Montgomery County Fairgrounds, Gaithersburg. 300 artists and craftsmen. Adults $3.50; under 12, free. 301/831-9191.

CHRISTMAS BAZAAR -- Friday, 7 to 10; Saturday, 10 to 3, St. Andrew the Apostle, 11602 Kemp Mill Rd., Silver Spring. Crafts, collectibles, baked goods and Christmas decorations. 384-5198.

ART AUCTION -- Friday, 8 (preview at 7), Mt. Vernon High School, 8515 Old Mount Vernon Rd., Alexandria. Refreshments, door prizes. $2. 780-2100.

HAYRIDES -- Friday, 7 and 8:30; Saturday and Sunday, 2, 3:30, 5, 7 and 8:30, Harmon's Hayrides, Meadow Acres Farm, Centreville, Va. Belgian drafthorse hayride, campfire time with hot cider and doughnuts. Reservations required. Hayrides (by hour), adults and teens $6; ages 12 and under $4; cider and doughnuts, $3 extra per person. Call 703/327- 6731.

ROCK CREEK HIKE -- Saturday, 9 to noon, Picnic Grove 6, Beach Drive, Rock Creek Park. Join a naturalist for a hike to learn about the park. 426-6829.

CHRISTMAS BAZAAR -- Saturday, 9 to 4; Sunday, 9 to 3, Church of the Annunciation, Parish Center, 3810 Massachusetts Ave. NW. Christmas articles, attic treasures, fruitcakes, jewelry, refreshments. 362-3323.

CHRISTMAS BAZAAR -- Saturday, 10 to 7; Sunday 8:30 to 2, Christ the King Church, 2301 Colston St., Silver Spring. Silent auction, attic treasures, gourmet foods, refreshments, raffle. 244-2874.

CHRISTMAS BOUTIQUE -- Saturday, 10 to 6; Sunday, 9 to 2, St. Mary's Church, 5222 Sideburn Rd., Fairfax (near GMU). Cake, pine cone wreaths, gifts. 323-5511.

ARTS AND CRAFTS FAIR -- Saturday, 10 to 4, Town Hall, 10812 Kenilworth Ave., Garrett Park, Md. (2 miles east of White Flint Mall). More than 50 craftsmen. 942-4388.

CHRISTMAS CRAFT FAIR -- Saturday, 10 to 5; Suday, noon to 5, Vienna Community Center, 120 Cherry St. SE. Northern Virginia Handcrafters Guild features stained glass, dolls, toys, porcelain and pottery. 928-8618.

RING AROUND THE TOWER -- Saturday, 10, Old Post Office, Tower, Pennsylvania Avenue and 12th Street NW. The National Park Service and Washington Ringing Society present a demonstration and talk on the art of bell ringing. 426-6700.

CRAFT FAIR AND BAKE SALE -- Saturday, 10 to 3, Gaywood Elementary School, 6701 97th Ave., Seabrook, Md. Homemade crafts, Christmas gifts, baked goods. 577-3215.

HOLIDAY CRAFT AND FOOD FAIR -- Saturday, 10 to 4, Montessori Country School, 621 Alabama Ave., Herndon. A wide variety of handiwork and children's books. 620-0057.

GRAY ELEPHANT SALE -- Saturday, 10 to 4, Forest Heights Municipal Building, 5508 Arapahoe Dr., Forest Heights, Md. Arts, crafts, plants, flea market. 839-1146.

HOLIDAY BAZAAR -- Saturday, 10 to 3, Bethesda Community School, 7500 Honeywell Lane (between Old Georgetown Road and Bradley Lane), Bethesda. Toys, pottery, floral arrangements, sweaters, ornaments, wood carvings. 652-0117.

OLD TOWN TOUR -- Saturday and Monday, 10:30 a.m.; Sunday, 2, Ramsay House Visitors Center. Retrace the steps of George Washington and Robert E. Lee with a colonial- attired guide through the cobblestoned streets of Old Town Alexandria. Adults $3; ages seven to 15, $1.50. 548-0100.

DECOY CARVING DEMONSTRATION -- Saturday-Sunday, 11 to 5, Audubon Naturalist Society, 8940 Jones Mill Rd., Chevy Chase. Seven award-winning artists demonstrate all phases of carving and painting. 652-9188.

POTTERY SHOW AND SALE -- Saturday, noon to 4, 1500 Merrimac Dr., Langley Park, Md. Pottery, demonstrations, refeshments, door prizes. 445-4508.

CHRISTMAS BAZAAR -- Saturday, 2 to 7, St. Barnabas Epsicopal Church, 14111 Oak Grove Rd., Upper Marlboro. Handiwork and Christmas items, baked goods, plants, attic treasures. 249-9671.

COWBOY DANCE -- Saturday, 8 to midnight, Potomac Center, 11315 Falls Rd., Rte. 189, Potomac. Instruction and dance to the sounds of Herb Fredericksen. $6. 301/840-2056.

DOLLS AND MINIATURES -- Sunday, 10 to 5, Charles W. Baldwin Hall, Generals Highway, Millersville, Md. Doll artisans and miniatures craftsmen exhibit their work. $2. Call 544-5423 for more information and directions.

CHILI COOKOFF -- Sunday, noon to 5, Springhill Lake Fountain Lodge, 6220 Springhall Dr., Greenbelt (next to Kenilworth- Greenbelt intersection). Country music, chili, jalapeno pepper eating contest. 459-8444.

ODWIRA CELEBRATION -- Sunday, 12:30 to 5, 1501 T St. SE. The Temple of Nyame presents an African Harvest ceremony, drumming and potluck dinner. Call 434-0261 or 678-1170.

CANDLEMAKING -- Sunday, 1 to 4, Sully Plantation, Sully Road, Chantilly. (Take U.S. 50 west to right on Sully Road; park entrance one mile on right). Learn the traditional way of making candles. 437-1794.

BOOK AND FLUTE PARTY -- Sunday, 2 to 4, 3125 Garfield St. NW. The Radcliffe Club presents a meeting with Nancy Toff, author of "The Flute Book: Complete Guide for Students and Performers." Three flutists provide musical entertainment. 833-2330.