Shoppers looking for the best discounts this holiday season won't be able to get them all on their own. They'll need a little help from social networking sites and their cellphones.

The technology behind these deals was already in place on Black Friday, when shoppers who checked in to a Hollister store using app FourSquare got an exclusive coupon for 20% off that could be scanned at checkout. Earlier, Radio Shack (RSH) offered $10 off a purchase of $40, and a 20% discount on all accessories, only to its Facebook fans.

Retailers have been experimenting for months with exclusive deals via apps and social media, but this is the first holiday season they ll be using those tactics, says Lynn Mettler, the founder of Step Ahead, a marketing firm in Mount Pleasant, S.C. And it s an important time for this push. More consumers plan to use technology to check off items on their holiday lists. The number of consumers using their phones to compare prices and find deals is expected to grow by 25% this year, according to the Mobile Marketing Association, while online and other non-store shopping is expected to grow 15%. Retailers are realizing they have to pay attention to this space, Mettler says.

For stores, pumping out promotions and deals via Facebook and Twitter has some inherent advantages. Other than labor, it s free, and if users pass the deals along by sharing or re-tweeting them, that's extra publicity for the retailer. Plus, by making followers and friends feel they re getting a deal that s not widely available, stores increase the likelihood that customers will bite, says Deborah Mitchell, executive director of the Center for Brand and Product Management at the University of Wisconsin-Madison. This time of year, it s almost a sport to brag about the deals you got, she says. They re playing on that feeling.

Still, it may be worth connecting with your favorite stores and brands. Here s how:

Check in When You Arrive

More than 2 million U.S. adults now use apps like Foursquare and Facebook Place to check in via smartphone when they arrive at a business. And deals and discounts for doing so have picked up this year, says Brad Spirrison, managing editor for review site Appolicious. The new deals section of the Facebook Place app includes 20% off at H&M, $10 off a $50 J.C. Penney purchase and 20% off select items at Macy s; among Foursquare s deals, Zales (ZLC) will offer $50 off a $300 purchase and American Eagle (AEO), 15% off. But if you re concerned about your privacy or just want to keep that holiday shopping trip to FAO Schwartz a secret these apps may not be for you. Some of them automatically broadcast your actions to your friends and followers on Facebook and Twitter, unless you specifically tell them not to.

Watch for Barcodes

Using a phone to acquire or redeem mobile coupons is the newest and fastest-growing area of mobile marketing. By 2011, some 3 billion mobile coupons will generate more than $87 billion in sales, according to Jupiter Research estimates. The trend has already taken hold at stores like Target and Toys 'R' Us, where customers can pull up coupons on their mobile phone and scan them in the store. Meanwhile, phone-scannable 2-D barcodes are starting to show up in magazines and billboards, and while most link to promotions or viral videos, according to code maker Nellymoser, some offer lucrative deals. Earlier this fall, Bluefly.com used a 2-D barcode in its TV advertisements that sent consumers to a $30 coupon on an order of $150 or more.

Friend on Facebook

Most mainstream brands have their own pages by now, says Mettler, but truly social media-savvy companies will offer more than just a constant stream of spam in your news feed. The product s main page and the tabs may offer deals: Cold Stone Creamery is offering $3 off an ice cream cake; Mimi s Caf has $5 off a $15 check. Some deals require you to do a little more than click. Old Navy offers a Barker s Bones game that has an animated dog dig users up a weekly discount. On its Groupon-like wishtogether tab, Sears fans can like daily deals such as a Garmin Nuvi for $90 instead of $130. If enough users participate, the deal becomes available for purchase.

Follow on Twitter

Pay attention to companies fast-moving feeds for exclusive sales, Mettler says. JetBlue and United post weekly Twitter-only fare sales -- a recent JetBlue sale offered a one-way San Francisco to Boston seat for $119 instead of $259, a 54% discount -- and Gap (GPS) recently alerted its followers to a one-day flash sale for 40% off all purchases (45% with a store credit card). Coupon sites such as RetailMeNot and Dealnews also maintain feeds to pass along the latest sales and coupons that come their way. And while actively using Twitter increases the chance you ll catch these fast-moving deals, you don t need an account to check a company's Twitter page. (Use Google (GOOG) to search for the company s name followed by on Twitter, and you ll find it.)