Are you cautiously, slowly sorting out how and how much to engage with your customers in social networks such as Facebook, and over smartphone apps. Well, lucky you. If your customers are teenage girls, though, and 72% of them are on Facebook, and 36% of them have a smartphone, you don't have the luxury of taking your dear sweet time.

That's the case for the innovative clothing retailer Wet Seal, which is years ahead of most companies in not just learning about online social networking with its customers, but getting results. Wet Seal was named the top innovator in the use of wireless technology at this year's InformationWeek 500 Conference. Shawn Keim, the company's director of development, spoke at the recent IW 500 event, and what follows are some of the extraordinary lessons he shared about engaging Wet Seal customers through these channels.

Wet Seal launched a tool in 2008 on its Web site that lets girls create outfits that combine different Wet Seal tops, bottoms, shoes, and accessories. That allows for user-generated content: Girls have created more than a half million outfits on the site, and they provide a stream of new--and credible--content for Wet Seal.

That application got a lot more interesting when, in 2009, Wet Seal embraced its “social merchandising” strategy that blends the Web strategy with Facebook and smartphones, beginning with the iPhone. (If this all sounds very faddish, read on for real results and lessons learned.)

In Facebook, Wet Seal's fan page offers a better way to share outfits that girls put together using Wet Seal clothing--sharing them not just with other Wet Seal shoppers, but all of a person’s Facebook friends.

On the iPhone, they can view those outfits, including while shopping in stores. They can enter a barcode number of a shirt into the iPhone app and see what outfits girls have put together around that shirt. Beginning this month, they can beta test an iPhone game that lets them choose what clothes they’d stock if they ran a Wet Seal store.

From the WetSeal.com Web site or Facebook page, girls can "shop with friends," connecting their sessions live so they show each other outfits.

Here are some hard results from Wet Seal's social merchandising efforts:

Shoppers using the outfit tool are 40% more likely to buy something, and buyers spend 20% more.

"Shop with friends" users become buyers at 2.5 times Wet Seal's average conversion rate online.

The iPhone app generates about 5% of Wet Seal's overall Web traffic, and the app has been downloaded more than 65,000 times.

Girls look at about 500,000 outfits a week with their iPhones -- traffic that spiked to about 750,000 a week the two weeks before back-to-school.

Facebook has become one of the largest marketing bases for store traffic, thanks to coupons and campaigns, and one of the biggest drivers of traffic to WetSeal.com