Black Friday exists for one reason: To get more people into stores and spending money.

But at the same time, the promotions surrounding it - special events, early morning shopping hours and a reputation for deals - have created a momentum of its own, making the day after Thanksgiving one of most-discussed retail day of the year.

Getting back to the reason: It’s the money. That day, 138 million shoppers will hit stores that day, according projections from the National Retail Federation.

And those shoppers will be opening their wallets: They spent an estimated $10.6 billion in 2009.

“This is a time when merchants make 30 to 35 percent of their sales for the year,” said Ida Hendrix, manager of Briarwood Mall.

Shoppers, meanwhile, respond to the efforts to get them into the stores by getting up early (or not going to bed until morning), standing in line and starting the buzz on special deals well before the day itself.

“We consider it an exciting time of the year and we love the energy on Black Friday,” Hendrix said.

She was speaking of mall staff, but the words also could describe the feelings of many shoppers.

Frank Guglielmi, a spokesperson for Meijer, agrees.

“There’s a happy feeling (among shoppers),” he said. “Black Friday has a level of excitement. There’s the thrill of the hunt that a lot of people experience.”

Area Meijer stores will stick to their 24-hour format through Thanksgiving. Special “doorbuster” sales also start today.

Then the store remains open into the wee hours of Black Friday, when those day’s sales start at 5 a.m., said Gugliemi.

“Since we’re open 24 hours, there’s no long lines at the doors, waiting for the key to turn,” he said, referring to the common practice by shoppers of lining up to assure they have access to limited quantity items.

But that doesn’t mean lines don’t form inside the stores.

“We’ll get lawn chairs set up along the open aisles,” as customer camp out, waiting for the sales to officially begin.

A holiday display welcomes shoppers at Briarwood Mall.

Angela J. Cesere | AnnArbor.com

The situation will be similar at area Walmart stores, including stores in Ypsilanti and Pittsfield, which also start their sales at 5 a.m.

Many retailers already are gauging customer response to their Black Friday deals, thanks to the flow of online information on their sales - including advance copies of ad promotions - that circulate weeks before the actual date.

While some retailers fight that practice, Meijer isn’t one of them, Gugliemi said.

The company started the practice in 2007, and continues it today. However, customers do need to register on a social media site to see them.

The social media strategy is blooming at Briarwood, too.

At Briarwood, 3 department stores will open at 4 a.m.: Macy’s, JC Penney and Sears. The rest of the mall opens at 5 a.m. (Sears, for the first time, also will be open today from 7 a.m. - noon.)

But, showing retailers’ increasing use of social media, JC Penney will open 30 minutes earlier for Briarwood’s followers on Facebook, said manager Ida Hendrix.

What are shoppers likely to find once the stores open?

Some national Black Friday retail sites say electronics and toys are likely to be big traffic drivers.

Others may be watching their phones for incoming alerts to timed deals. Briarwood, one of the Simon Properties malls across the U.S., will offer that company’s iPhone app to tout retailer offers.

And some may notice higher quantities of sale-priced items and gift-card-with-purchase deals.

The key to Black Friday, Gugliemi said, is “read the ads closely and understand what the restrictions are. Every retailer has some.”

And if a shopper is in a store for a particular item, try to engage staff to see how many items are available and whether it’s worth standing in line.

“A store manager should be able to tell them yes or no,” Gugliemi said.

Meanwhile, at other locations in Ann Arbor, many other shopping centers and downtowns are gearing up for traffic increases, as people use a day off from work and the official launch of the holiday season to both browse and buy during normal business hours.

“We’ll be packed,” said Jim Chaconas, a partner in Westgate Mall on Ann Arbor’s west side.

Holiday decorations went up on Monday, and the retailers in the center - a mix of national stores and locally owned independents and franchises are bracing for heavy traffic.

TJ Maxx always draws a crowd, even without early hours, Chaconas said, and the restaurants - like Quarter Bistro and Zingerman’s Roadhouse - also are destination stops for shoppers. Combined, Chaconas said, the retailers give the center more of a “village” feel than a typical strip center.

So far, the center’s retailers say their sales are stronger than 2009 as they head into Black Friday, Chaconas added.