DO YOU KNOW anyone who has the flea bug - an uncontrollable urge to collect, a passion for haggling and a weakness for secondhand and antique goods?

The common remedy is frequent visits to one of the dozen or so indoor and outdoor flea markets in the area.

Where else can you find, side by side, a set of used ear plugs (50 cents), an Art Deco hanging birdcage ($20, sans bird), an ensemble of vintage extra-large dress pants ($25), a pair of delicate gold Philadelphia Centennial Exposition cufflinks ($100) and a slightly potato-stained Vego-Matic (1)?

While flea markets vary in size from the mammoth outdoor Sunday market at the Edmondson Drive-In Theater in Catonsville to the small indoor ones held weekends at several local shopping malls, the rules are the same: Merchandise runs from out-of-date housewares, beer cans, campaign buttons and schlock art to bona fide antiques (a century old or older), and dickering's the name of the game.

The clientele is as varied as the items on sale: young couples seeking to furnish a house, older people lingering over nostalgia items that were popular in their youth, indiscriminate rubbish-rakers and collectors of Nazi souvenirs, dolls, unusual old toothbrushes and almost anything else that's collectable.

A common sympton is the thrill of the chase, the search for a "sleeper" worth more than the vendor realizes. This is fed by the innumerable stories passed from one bargain-hunter to another about someone who bought a $4,000 tapestry for $27, or a priceless porcelain vase for $10. There are two distinct tactics: Some customers, and many dealers, go early to snap up choice items before they're gone, while others go late in the day, feeling that vendors who don't want to pack their wares and lug them home will be easier marks.

Barry Hayman, who ran the Barracks Row Flea Market last year, offers novice hagglers some tips:

"If someone comes in dripping with gold, I won't discount an item like I would to a poorer-looking student type," he said. "The way someone approaches me matters, too - if he's polite and sincere and I get a good first impression I may come down in price. Then there're what I call the price butchers, who obnoxiously offer you $10 for something you've got marked for $100. For those people I might raise the price."

But asking a dealer, "Is that the best you can do?" on a price never hurts, for many vendors admit that they'll almost always go down at least 10 per cent on an item.

On something expensive, such as a gold watch or a Chippendale desk, it's wise to get a written guarantee that the item is what the dealer claims. The dealers themselves range from hard-core profit-seekers through hobbyists to those who just enjoy the give-and-take.

"In my regular job I don't get to see or talk to people too much," said a 39-year-old press operator from Sterling. "I like the bargaining the best, and I just enjoy people."

"Selling is like a disease for me that just gets worse and worse," Peg Johnson said with a laugh. During the week the Reston woman is an administrative aide, and she explained how the bug bit her: "I just kept collecting to the point that I had no room for anything, so I started selling."

"I'm just in it for the money," said a Loudoun County TV technician, adding that he preferred to remain anoymous for tax reasons. "I deal in what I call junk art, and I can make about $200 on a weekend by buying something for $5 and selling it for $100." Some proprietors, like Georgetown Flea Market's Mike Sussman, invite people to gather up used items with their neighbors and have their garage sales at a flea market.

"For the $12 rental fee you can make money and have an interesting, fun day," he said. "The idea is not to press for top dollar, but to take home as little as possible, recycle your things and have a good time."

Since fall is traditionally a time when closets are cleaned out, people are back from vacations and the outdoor flea markets are finishing up in a blaze of glory, both seasoned and novice flea marketers claim it's the best bargain season.

Families combined a scenic trip to Skyline Drive with a stop at the Manassas or Front Royal market, and on rainy weekends parents can spend an entire free and interesting day with the kids retelling stories of their youth prompted by finding the blue glass Shirley Temple dishes that used to come as premiums in Mother's Oats, or explaining patiently what that funny-looking manual can-opener used to be used for.

Most outdoor markets are held from mid-March or early April until the last weekend in October or the first weekend in November, weather permitting; most indoor markets are open year-round. Check the weekend classified section under "Antiques and Collectibles" for special, one-time markets.

Following are some of the area's regularly scheduled flea market: