While you're decking the halls and trimming the tree, don't forget your- self. This ceramic popcorn and cranberry necklace is so real it will fool even the birds. Artist C.O. Day of McLean makes her molds to resemble the real stuff. She even hand- finishes each kernel with dental tools. Cranberries are easier. So are M & Ms, pretzels, pickles and hot peppers, all of which also come with matching earrings. There's a special creation for mothers-to-be: a necklace of pickles and ice cream cones.

Popcorn necklace. Three lengths: $40, $45 and $50. Earrings. $10 a pair. Chocolate Moose, 1800 M St. NW. 463- 0992. Also at Foliograph, Tysons Corner Center, McLean. 893-2610. IN THE CAN

Kids of all ages adore squirting these colorful streamers about. (Make sure they practice outside first; it's not easy to squirt a straight line.) These are a sure way to have as much fun getting ready for the party as enjoying the event itself. Also, consider this a creative answer to what even young children can do to celebrate the New Year. You may want to keep a can on hand for birthdays, anniversaries, Fourth of July celebrations or other extravaganzas.

Crazy Strings. $3.50 a can (green, yellow, orange and pink). Art Explosion, Montgomery Mall. 365-3669. Fair Oaks Mall, Fairfax. 385-3393. CHECKMATE

Take this one for the road and you won't be sorry: your very own alcohol tester. This example of technology-to-go tells you whether you and your friends are sober enough to leave the party and drive home. The six-inch-long unit indicates concentration of alcohol on your breath with a red light for fail, an amber light to warn and a green light to pass with flying colors. It's a good gift to give to a loved one, a perfect hostess or your thoughtful barkeeps. It could be the most important gift you give.

Alcohol tester. $70, including 12-volt car adapter and batteries. At all area Hoffritz stores. NOVEL IDEA

Here's a chance to let your favorite child be the lead character in his or her own book. Bloomingdale's has installed a Commodore computer at each of its stores (and a computer operator to help all of us computer-illiterate but well-mean aunts, uncles and grandparents). All you do is fill in the blanks with the child's name, pets, friends, school information, neighborhood and birth date, and the computer does the rest. You end up with a bound 32-page, illustrated 81/2- by-11 hardback with colorful cover suitable for children ages 1-9. There are three books: The Mystery of Scented Mountain, The Holiday Dragon The Greatest Circus Story Ever Told. minutes with the personalized prose. P.S. Last-minute Santas: They'll be turning out great works till 6 p.m. Christmas Eve. Build a Book. $19.95 each. Bloomingdale's White Flint and Tysons' Corner.