Wal-Mart, the nation's largest retailer, developed store-specific plans for all its U.S. locations in an attempt to reduce congestion following last year's trampling death of a temporary maintenance worker at its store in Valley Stream, N.Y.

The National Retail Federation, the world's largest retail trade association, also issued a set of crowd management guidelines.

There were no immediate reports of problems in Los Angeles County stores.

"Everybody's a lot calmer. Everybody's a lot happier," Edward Moriarty, the general manager of the Best Buy in Atwater Village, told KCAL9. "We're handing out coffee, making sure they get maps so they know where to go."

The Best Buy in West Los Angeles was arranged differently than last year so customers could wander in and out more freely, general manager Daniel Park told the Los Angeles Times.

When the store opened at 5 a.m., just 20 customers were allowed every 20 seconds in an effort to prevent overcrowding, The Times reported.

In Harbor Gateway, about 5,000 people were lined up outside the Wal-Mart store before 5 a.m., police told the Daily Breeze.

Officers and extra security helped ensure there were no problems, according to the Daily Breeze.

The line outside the Target store in Carson spilled on to Sepulveda Boulevard,

Black Friday is characterized by early openings of stores and shoppers lining up even earlier to get the best opportunity for items discounted by retailers to lure them into stores.

With the Black Friday practice of retailers both limiting the time the "door buster" low prices are in effect and the supply of particular items, there could be "a bit more aggression" by shoppers this year," said Lars Perner, an assistant professor of clinical marketing at USC's Marshall School of Business.

"In the past, if you didn't get a good deal, that was fine, you might buy something else," Perner told City News Service. "But this year when money is tighter and people are counting to a greater extent to finding low prices, I think there can be more frustration."

A survey conducted for the International Council of Shopping Centers, a shopping center trade association, found that 26 percent of the U.S. households questioned plan to shop today, with 36.2 percent of shoppers planning to arrive between 4 a.m. and 8 a.m., 28 percent between 8 a.m. and noon and nearly 18 percent between midnight and 4 a.m.

However, Black Friday is not the day when the most purchases are made. That distinction is usually claimed by the last Saturday before Christmas.

This year's hot toys include 7n1 Maxus Drago Bakugan; Crayon Town; Disney Netpal; Girl Gourmet Sweets Candy Jewel Factory; Nanovor Nanoscope; the "Just One Kiss" Tiana doll from the Disney animated film "The Princess and the Frog"; Printies Design Studio; the Twilight Deluxe Edition of Scene It?; Star Wars Battle of Endor; Star Wars Clone Turbo Tank; Zhu Zhu Pets; and the Zippity Learning System, according to Toy Wishes Magazine and the International Council of Shopping Centers.

Popular electronic items include the Amazon Kindle and Sony Reader e- readers; the video games Beatles Rock Band and DJ Hero; the Xbox 360, PS3 and Wii video game consoles and the iPod Nano MP3 player.

Women's clothing items in demand include social occasion dresses, plush long cozy sweaters, leather jackets and zip-front hooded sweatshirts. Top men's choices include faux leather jackets, fluffy robes and flannel shirts.

The term Black Friday in connection with the day after Thanksgiving has several origins. The earliest comes from the mid-1960s from the Philadelphia Police Department because of the heavy traffic caused by shoppers.

An explanation from the early 1980s ties it to the accounting practice of using black ink to denote profits, with the day after Thanksgiving beginning the period where some retailers achieve a profit on the day after operating at a loss earlier in the year.