The first spot that Krista Collins Checks when she enters her neighborhood Safeway supermarket in Silver Spring is the corner where beef packages have been marked down for quick sale.

"It's the only time that we eat beef," said Collins, pushing a grocery cart that carried her 2-year-old daughter Jessica and her bargain of the day -- a flank steak that had been slashed 24 percent, from $5.25 to $4.

The steak was on sale because it was one day beyond the "sell date" stamped on the label, the date by which the item is supposed to be sold to give the consumer maximum safety and freshness.

Marking down prices is one of the methods used by supermarkets managers to clear out leftover foods -- items that are still good but can't be sold at regular prices because they are past their prime or because the containers have suffered some minor damage.

When the foods can't be sold, they may be given away to charitable institutions. When that isn't possible, because of health questions, the leftover foods are thrown away.

An estimated $660 worth of food is discarded every week by the average supermarket, according to industry officials. The type and amount of leftovers vary from store to store, and the manner in which one store disposes of its leftovers may be different from another. Some supermarkets, for example, don't ever reduce their meat prices. When the meat is past the sell date, they simply dump it.

Although managers and the chains are reluctant to discuss the value or the volume of the throwaways, some are willing to describe the types of food and the reasons why they are thrown away.

"We dump all poultry and dairy products when they are out of date. We don't sell them after that because of the potential health hazards," said Larry Johnson, a representative of Safeway. Produce, bread and beef also are discarded if they don't sell after one day on the half-price shelf.

Shoppers who want to take advantage of reduced prices should ask the manager what products are available and when they are most likely to be marked down. Generally, however, early morning hours are the best time for finding reduced prices on meat, bread, produce, canned goods and other items.

Evenings, two to three hours before the store normally closes, are the best for finding deli meats, salads and baked goods.

For shoppers such as Collins, who buys for her husband and two small children, the markdowns represent a welcome relief from the continuing food-price spiral. To take advantage of such bonanzas, she shops early -- usually before 10 a.m.

"If you wait, there won't be any [beef on sale] left," she said.

Other bargains that Collins regularly seeks out at her store include:

Produce marked down to half price because of discoloration or mottled appearance. Such choices one day last week incluced a bag of squash for 59 cents and a package of pears for 69 cents.

Canned goods and miscellaneous groceries marked down to half price because of slight damage to the container. The 15 items included a can of green beans that had been reduced from 45 to 23 cents because of some minor dents. A 5-pound sack of flour had been marked down for $1,59 to 80 cents because of a rip.

Bread and baked goods marked down to half price because they are past the sell date. The display filled two shopping carts and included a range of products, from whole wheat bread to jelly-filled donuts.

Ann Johnson, manager of the Silver Spring Safeway at 9440 Georgia Ave. NW has learned to expect a small rush of bargain hunters when her store opens at 8 a.m. "There are four or five regulars, including one elderly man who comes to see what meat we have marked down. This morning he bought four packages, including two ground beef," Johnson said.

Some reduced-price foods are available every day at Johnson's store, but she said that usually there are more on Mondays and Wednesdays and fewer on Thursdays.

Bargain buys also are available late in the day at supermarkets outfitted with delicatessens or bakeries. Fried chicken, barbecued pork chops and other foods prepared in the store early in the morning generally must sell that day or be thrown out. So if the foods haven't been sold by about 8 p.m., the store may reduce the price.

Salads and desserts in the deli case also usually are marked down for quick sale when they are approaching the end of their shelf life.

According to surveys by the Food Marketing Institute, a trade group of retail stores, the average U.S. supermarket sells about $100,000 a week worth of merchandise.

Those sales are based on the supermarketing system, in which foods commonly are transported from the company warehouse to the supermarket. Once the goods are in the supermarket, it is up to the store management to dispose of them as profitably as possible. The overwhelming majority are sold at regular prices.

In some cases, when the food products are not sold, the store can get full credit by returning them to the supplier. Pepperidge Farms, for example, picks up any unsold merchandise from stores. So does Pepsi Cola. But companies that do this represent less than 10 percent of a supermarket's inventory of food products.

The other 90 percent must be sold. In a few cases -- less than 1 percent of the total sales, according to some estimates -- unsold food is offered at reduced prices or dumped.

Because of the cost of transportation, chains generally never take foods from the supermarket back to the warehouse. "It just doesn't pay to do that," Johnson said.

Safeway, like some other local food stores, also contributed some unsold products to nonprofit organizations. This month, the chain has given 3,800 pounds of food to the Capital Area Community Food Bank, which serves as a clearinghouse and distributes as a clearinghouse and distributes food to 104 charities in the Washington area.

Some foods are more likely to be dumped than others.

Milk, for example, generally has a shelf life of about one week. If the warehouse computer mistakenly sends too much milk to a supermarket, the unsold cartons and jugs may end up being thrown away.

Produce has an even shorter life.

"Sometimes, with lettuce, we can recrisp it and sell it the next day," said Johnson. But when the fresh fruits and vegatables reach a certain point, they are tossed into the garbage disposal in the back of the store.

And the meat that nobody will buy even at the specially reduced prices?

"It goes into the meat bin with the meat trimmings to be picked up by the bone and fat company," Johnson said. "I don't know what they do with it -- maybe make dog food."