The Foursquare interface shown on a BlackBerry

Whether you’ve made up your mind about the usefulness of social media or not, the numbers are staggering. In January 2009, there were 42 million Facebook users in the United States. By January 2010, there were 103 million. And while the growth of Twitter users is slowing, there are still 64 million tweets every day. But the real cutting edge is Foursquare. Read on.

When Financial & Insurance Conference Planners held its Education Forum in St. Louis in June, one of the breakout sessions was hosted by Brian Hall, chief marketing officer for the St. Louis Convention and Visitors Commission, and a former social media skeptic. “I thought it was a place for kids to play,” he says. And now? “I’m a believer.”

The St. Louis CVC has signed on with global PR firm Weber Shandwick to guide and monitor its social media presence. “We wanted to respond to what’s out there,” Hall explained. “It’s vital to an organization.” Three of Weber Shandwick’s social media experts delivered a breakout session at the FICP Forum called “Social Media Strategies that Lead to Results.”

Check Out the Checkins
If you’re using Foursquare, you’re really a social media pioneer. “Location-based apps have the most buzz right now,” said Weber Shandwick’s Sean Hixson, group manager. Download Foursquare to your smart phone, then press “check-in” whenever you go somewhere—your meeting hotel, the local Starbucks, the airport. Users can leave tips about any of the locations they visit, and the whole thing is also a game in which you earn badges for visiting certain types of places and become the “mayor” of a particular place by being the person who has checked in there most often.

Badges? The mayor? Seems a little year-after-college, no? Yes, but there are ever-growing business apps as well. Visit the businesses page  at the Foursquare Web site for an instant sampling of how businesses in your area are using it. (If I check in at the Kate Spade store in my local mall, for example, I get 15 percent off.) For hotels and other meeting suppliers, checkins can build awareness and drive traffic and loyalty when some type of reward is offered.

There are applications for events as well. At a trade show, Foursquare users might earn badges for checking in at particular booths. At the now-legendary annual South by Southwest Music & Media Festival in Austin, Texas, Spin magazine awarded badges to attendees who checked in at three performances of bands with an animal in their names or for checking in at performances of bands that editors recommended.

The possibilities for increasing engagement, particularly at large events, are enormous. Foursquare marked its 2 millionth user in July, and is adding approximately 15,000 worldwide users per day.

Of course, that’s nothing like Facebook’s 400 million worldwide users. Bob Rybarczyk, vice president of Weber Shandwick pointed out that content sharing (links, photos, videos) on Facebook is rising as well, from 1 billion items shared per week in July 2009 to 5 billion in February 2010. Many people start their days logging onto Facebook. His advice for your Facebook page: People want a little “extra” something if they “like” your page. That could be a discount, some newsworthy information that they’re among the first to know, or a game. Another major point to consider: Make any content you want to share friendly for mobile devices. Smart phones are where it’s all going.

And then there’s Twitter, a form of “microblogging,” said Weber Shandwick’s Meredith Brengle, digital communications supervisor. “It’s instant engagement,” she said, and a way to “gauge sentiment on your brand”—whether that brand is a hotel or a meeting. Brengle advised setting up a “hashtag” as part of the meeting-planning process so that attendees can start interacting about the meeting before it happens, while it’s going on, and after they’re back in their offices. A hashtag collects all tweets about a particular topic, making them easily searchable.