The wary woman slowly circled the rusty cast-iron bathtub, sitting like a boat in dry dock in Susan Pepper's Arlington driveway. Carefully, the woman inspected the flaking off white enamel and checked to see if the ball-and-claw feet were still secure.

Spying a potential buyer, Pepper eased through an obstacle course of tables laden with six pairs of disintegrating leather ice skates, old car radios, her ex-husband's fishing trophy, a Day-Glo green plastic coat and a set of Ronald McDonald glasses.

She sidled up and started her pitch.

"Listen," said Pepper, fending off the early morning heat with a wine cooler, "you can put it in your living room and fill it with big goldfish. It would make a great art deco sofa. . . . Just cut out the side, paint the outside yellow and fill it with batik pillows. It would be precious."

"How much?" asked the shopper.

"A hundred dollars or best offer," said Pepper.

"Maybe I'll come back later," said the shopper, with a knowing glance that her best offer would look better by the end of the day.

But the Ronald McDonald glasses were moving briskly at 10 cents apiece, while shot glasses were going for a nickel apiece. And one 13-year-old girl couldn't resist a pair of black-silk pumps, vintage 1950, with a lacy black rose atop each toe and a price tag of 25 cents.

Pepper, 34, wearing a hot pink Izod T-shirt and cutoff jeans, hawked her wares in bare feet with a steady stream of one-liners.

"If you needed a plastic coast, would you pay 15 cents?" she asked one owman who took a second look at the clothes where the shiny green blazer was hanging.

"The trophy with the fish on it belonged to my first husband," she told some other shoppers. "I'm giving it away."

The garage sale. It's a summer pastime, a suburban molt, as attics and basements from the posh nieghborhoods of McLean to the tidy subdivisions of Herndon bring forth lifetimes of trash and treasure. Garage sales are so popular, in fact, that on most weekends, browsers can take their choice of wares in at least 100 back yards all over Northern Virginia.

Just as the pace began to fall at Pepper's, a white Trans-Am with mag cheels pulled up to the curb. yout came Mike McFall, a lanky man in denim, led by his wife Masako, a short, stocky woman with jet black hair and the eye of a hawk when it comes to spotting gems at yard sales.

"My wife just loves to go to garage sales," McFall said. "Every Saturday morning I get to drive her all over Northern Virginia. We usually come home with a couple of bags of things we really don't need, and once in a while we get some nice stiff."

This time it was an electric popcorn maker in the shape of a covered wagon. The machine went for $3 and Mike McFall got to lug it home.

Pepper organized her two-day yard sale with two neighbors. They wanted to clean out garages.

"I just got married six months ago and my husband and I just never got the chance to combine our things," she explained. "These are the left overs. I figure we can make at last $600."

Pepper's sale was listed to begin at 9 a.m., but the first knocks on her door came at 8, from people who take their junk seriously. In fact, yard sale cognoscenti report that Northern Virginia has a platoon of about two dozen hard-core shoppers who do the circuit every weekend.

"We see the same people all the time," said one regular, Cindy Collegeman, 33, who describes herself as "a patron of yard sales."

It was nearing noon, the best buys of the day were already packed away, and Collegeman was sitting in a driveway up the street from Pepper's, where W.T. Howell was having his annual "clean-out-the-garage sale." Together with fellow addict David Zimmerman, 34, Collegeman grazes through suburban yards with the zeal of a gambler in Reno. She's been on the trial every Saturday morning for the past 15 years.

"It takes discipline," Collegeman said. "We're on the road by 9 a.m. You snooze, you lose. Nd you have to avoid the temptation to hang around sales where all they have is early American grotesque. With only two hours before the good stuff is gone, you have to maximize your time."

For the team of Collegeman and Zimmerman, the yard sale tour is practical entertainment. Collegeman said she furnished her apartment entirely with yard sale finds. Occasionally, she'll find a good piece of china for her Roseville collection. By the time Zimmerman had made it to the Howell backyard, he already had picked up two books about Judaism for his father's birthday.

Then there's the yard sale lore about valuable items bought for a song or the pieces of junk that seem to have a homing instinct.

Take Collegeman's friend, who once bought a watch for $15 and took it to a jeweler to see what she had bought. It was appraised at $4,200, thanks to the 24-karat gold band and the ruby stem.

Then there's the story about the orange juice maker that came back. For her wedding in 1968, a friend gave Collegeman an electric jucier. A couple of years later, Collegeman gave the jucier to her sister in Maryland. Some time later, her sister donated it to a white elephant sale at a local elementary school.

Collegeman, a graphic designer, was working at the school on a poster project when the jucier came up for sale.

"It looked like such a perfect thing," she recalled. "So I bought it. At $3 it was the buy of the day."

But the tale doesn't end there. Two years ago, Collegeman had a yard sale of her own and sole the same old jucier to the woman who gave it to her in 1968.

"It becme a standard joke," she said.

But the main attraction at the Howell yard sale was not juciers or books or the standard fare of Christmas decorations or glass ashtrays with hand-painted leaping sailfish. It was a 1962 Olds 98, red on white with a red interior, in mint condition, the humming of its eight cyclinder engine providing backyard music for the yard sale.

Every year at garage-sale time, Howell pulls the Olds, out of the garage and onto his driveway, a kind of come-on for shoppers. And while he will be glad to sell you a set of tire chains, a sump pump or a few quarts of leftover paint, the Olds is not for sale.

"It has 7,000 miles and hasn't been on the road since 1970," said Howell, a retired truck mechanic. "It's not for sale. I don't need the money."

While Howell was dealing mostly in old auto parts and hardware store leftovers, his neighbors across the driveway were holding a companion sale with a different flavor. Rather than grease guns, the two gray-haired women were dealing in old dresses, glassware, fine china and one gray toupe.

Brocade dresses and sleeveless print suits hanging from a clothesline were going for $2 to $5. A set of four glass shrimp bowls was selling for $3, and a "daisy button" candle holder, made of violet glass, was tagged at $14.

While the ladies were keeping close track of all sales, meticulously marking each transaction in a ledger book, Howell was stuffing greenbacks in his pocket, rarely taking time to count his profit.

"I don't need money," he said. "If I did I'd sell this house for $220,000. I just want to get rid of all this stuff so I have room to put my car back in the garage."