A vanilla cupcake with blueberry butter-cream frosting sealed the deal on Foursquare for New Yorker Twanna Hines. A blogger who writes about dating and relationships, Hines had already been using Foursquare, a social media app which asks people to check in on their phone each time they switch locations. Noting businesses people were frequenting, she would use the information as a way to alert followers to her picks for places to mix and mingle.

When Hines walked into a local bakery, Butter Lane, a few months ago, she got a message upon checking into Foursquare. As one of the first 10 users to visit that day, she was entitled to a cupcake, gratis. Now, Hines is a Butter Lane regular both for the cupcakes and the offers the bakery gives her. It's very rare that I don't go and get a free cupcake, she says.

Got a social media app? Look for a deal. Apps that track people s location are catching on, from Foursquare to Gowalla, to MyTown and Looptstar. In response, the app companies are teaming up with retailers and other businesses to increase exposure for the apps and to win customer loyalties for both parties. In late July, Chili's began offering free chips and salsa to Foursquare users who check-in at the restaurant chain. Startup game Scvngr offers a mobile coupon for $10 off a $20 Journeys's purchase to players who ace trivia games and other challenges. Looptstar sends a Gap coupon good for 25% off to users after they check into the store twice.

Just 1% of U.S. adults check-in more than once a week to location-based apps, according to market research firm Forrester Research. But companies are paying attention. Between public feeds, in-app networks and ties to other social sites such as Twitter and Facebook, checking in is a noticeable action one that real-world discounts entice consumers to do repeatedly. As a business, you can't ask for anything better than that advertisement, says Lyn Mettler, the founder of Step Ahead, a marketing firm in Mount Pleasant, S.C. This could be one of the most powerful tools of driving traffic.

Here's how deal-hunting consumers can take advantage:

Compare apps

If it s deals you re looking for, one of the more than 700 coupon-specific apps is likely to be a better source, says Brad Spirrison, the managing editor for review site Appolicious. Group buying site Groupon.com launched an app earlier this summer that lets users hunt for nearby deals. Most of the location-based apps perks are still virtual ones.

Commit to checking in

Some businesses offer extra discounts to the person who checks in most frequently at a particular location, Mettler says. In some cases, deals are only available to that what the apps are dubbing owner, mayor, boss or top visitor. For example, 232 participating Carrabba s Italian Grill locations offers a free dessert to the Foursquare mayor when he or she dines there. Each location has its own mayor, so it s worth it to be loyal to an individual store as well as the brand, she says.

But competition to get (and stay) on top can be fierce, especially since some companies allow employees to stay in the running. Assess whether the perks are good enough to justify the effort and expense.

Check surrounding businesses

Checking in doesn't just alert you to deals at that location. If a competing bar down the street has a happy hour special or a nearby store offers a deal, you'll hear about that, too, Hines says. Use that feature as a quick way to compare prices.

Merge loyalty rewards

Location-based apps aren t the only ones offering rewards for checking in. TopGuest, a reward program that monitors location apps, offers bonus points in partner hotel programs. If you check in on one of the apps at a Holiday Inn, for example, TopGuest will reward you extra points. Startup WeReward offers points redeemable for cash when users check in to partner businesses on Foursquare and offer a photo as proof of their visit. (Domino s Pizza is currently offering 25 points per visit. Earning 1,000 gets you $10.) The latest version of app CardStar calls up your store loyalty card barcode of when you check into a location on Foursquare.

Brands are getting in on the game, too. Pepsi Loot app tracks nearby stores that sell the brand s drinks, offering a point per purchase toward music downloads and other rewards. Starbucks has an app version of its loyalty card /spending/deals/should-you-be-true-to-your-retailer/, which provides a free drink after 15 paid visits.

Play the field

There s no reason someone can t have several of the free location-based apps on their phone, but participating in more than one is a drain on time, Spirrison says. Scvngr, for example, asks users to complete challenges to earn points, while MyTown has a game component where people buy, sell and trade virtual items to unlock new levels. You want to pick and choose one or two to invest in, he says.

Mind privacy

Read the app s privacy policy to see how it shares information in your profile and that you post, says Paul Stephens, the director of policy and advocacy for the Privacy Rights Clearinghouse, a nonprofit consumer advocacy group. Tweak the privacy settings if possible to limit who sees your check-ins. From a marketing standpoint, location-based apps give businesses more information about your shopping habits. You don t want to give a company any more data than it absolutely has to have on you, he says. There could also be security concerns, such as leaving your home open to burglars, for example, or aiding a stalker.