The shopping hordes that cruised shopping mall parking lots for spaces during yesterday's Washington's Birthday sales could have spent less time burning gasoline and more time blowing money if they had known Dot Lewis's system.

Using the system, Dot Lewis, her husband and their 13-year-old son John, who live in Falls Church, found a parking space at Tysons Corner shopping center: in 10 minutes. That was at noon; in that same parking lot, it took Jim Martin of Vethesda, who doesn't know about the system, 45 minutes to park.

The way Dot Lewis does it is this: She has her husband drop her off at a main entrance, she spots a shopper leaving the mall and then she follows that shopper to his or her car. Ed Lewis trails his wife in their car.

Dot Lewis was shopping for a "$600 to $900 mink coat" that her husband has been promising to buy her for five years. Ed Lewis said he was skeptical his wife could find a coat that would suit them both.

He was right. The Lewis family bought a $6.50 address book, a hamburger, a roast beef sandwich and an ice-cream cone.

In the shoulder-to-shopping bag crowds that choked area shopping centers and downtown stores yesterday, shoppers searched for bargains on items ranging from minks to a 38 cent breakfast.

For the breakfast, which included two scrambled eggs, toast, jelly and coffee and for other bagrains offered at area Montgomery Ward stores from 8 a.m. to 10 a.m. yesterday, shoppers arrived early. At the Gaithersburg store, an employe in the auto department said there were about 100 shoppers waiting outside for doors to open

When the doors did open, the employe said, "It was like you yelled 'free' and they all charged." More than 200 cases of oil at a 35 percent discount moved in less than two hours, he said.

Arthur Crown, a Washington Plumber who wore a gray suit and bought his wife a white skirt at the downtown Hecht Company store yesterday afternoon, was one of those who fought crowds between 8 a.m. and 10 in a Montgomery Ward store.

He waited in line 25 minutes to buy a case of oil. He waited in line 25 minutes to buy some 120-size film for his wife. When he got to the film counter, he said he was told it wasn't available. Afterchecking with his wife, he found out that what she wanted was 110 film. He did not return to stand in line.

Despite the lines and the crowds, Crown said he enjoyed shopping.

Not so Demosthenes Skouzes, a retired restaurateur who sat yesterday on a wicker-back chair on the fifth floor of Woodward & Lothrop downtown as his wife looked for dresses. He complained briefly, "She shops and I sit."

The people who come out on Washington's Birthday, according to several sales clerks interviewed yesterday, are "a lot of lookers." Kevin Krause, assistant manager at Britches Great Outdoors at Tysons Corner, said customers are "bargain hunters. People want to spend time comparing prices people try to talk you down on something not for sale."

A woman named Jill, who works at the Georgetown Cotton & Company shoe and clothing store at Tysons Corner, offered an insight into the buying psychology on Washington's Birthday.

She explained it standing near a large pile of right-footed shoes and boots. A crowd of people picked through the shoes and boots beneath a sign that said: "Rummage. Find Right, We'll Get The Left."

"It's funny," Jill said, "if you set those shoes up in a line, people will pass right by. But if you throw them in a pile people go nuts."

Steve Bayliss, manager of Georgetown Cotton & Company, said the pile of shoes and boots accounted for the sale of about 250 pairs yesterday.