Let’s say you want to reach young people. Maybe you have a product or service to sell, an organization or cause to promote, or a celebrity or politician to publicize.

You’ve probably heard about instant messaging, or IM. It’s a way to communicate instantaneously, or in “real time,” using a computer or computerized device. Despite the fact that IM has been around for nearly a decade now, it’s all the rage among the 18- to 27-year-old Gen Y crowd, a key demographic. Its popularity is even approaching that of e-mail. According to a recent survey by the Pew Internet & American Life Project, 46 percent of Gen Yers use IM more than e-mail. Why not harness the immediacy of IM to spread your message?

Because that would be a really bad idea.

So says Sean Carton, and he should know. Carton is a founder and “chief experience officer” at Carton Donofrio Partners, Inc. (http://www.cartondonofrio.com), an advertising and interactive media consulting firm in Baltimore. He is also dean of the School of Design and Communication at Philadelphia University and author of eight books about technology.

Although he has some reservations about using IM to start customer relationships, Carton does have some good ideas about how you can use it to create or strengthen client or customer loyalty.

What you first have to do is understand the differences between how people use IM and how they use other communication media. At first glance, you might think that IM is like e-mail, with people typing messages to each other. But in actuality, it’s really more like talking on a cell phone.

People react as negatively to unwanted instant messages as they do to receiving cell phone calls from strangers who are trying to push information in their face. “Instant messaging is about communicating one on one with people you trust, with friends,” says Carton. “It’s a personal experience.”

As hated as unsolicited commercial e-mail is for most people, unsolicited IM pitches would be a thousand times worse. If you want to create instant enemies, buy a list of IM handles. On the other hand, if you want to build friendly relationships using technology a la mode, use IM to make yourself or your organization available at all times to those interested in what you have to offer.

IM can be a quick and convenient way for people to get answers from your marketing or customer service department. It’s particularly appropriate for organizations that already have a strong online presence, from airlines to universities.

Studies have shown that e-commerce sites often lose sales because customers can’t get their questions answered quickly. With IM, people don’t have to go offline and slog through a voice mail menu or send an e-mail and cool their heels until it’s returned. They can also IM at the office without having others overhear them.

For organizations, IM automatically creates a written transcript of the interaction between a customer and a service agent. This can enhance quality control because these transcripts are easier to archive and search than recordings of phone conversations.

Just as with phone support, though, you have to increase staff to handle the message volume and to be prepared for spikes during busy periods surrounding product releases or holidays. People engaging in instant messaging expect instant results; not being able to come through with the goods would defeat your purpose. To avoid this, IM service personnel could have scripted answers available for the most frequently asked questions. This would allow them to quickly copy and paste responses or to post them by pressing predefined function keys.

A further, if riskier, step toward efficiency is setting up an IM auto-responding bot, or intelligent agent, to provide canned answers based on the questions asked. This can save you money. BotKnowledge (http://www.botknowledge.com), A.L.I.C.E. Artificial Intelligent Foundation (http://www.alicebot.org), and Pandorabots (http://www.pandorabots.com) are three companies that offer these devices; visit their Web sites to learn more about bots and to see them in action.

There are caveats, of course. No intelligent agent can handle unusual questions or situations as well as, or be as friendly as, a person. Bot stupidity is the IM equivalent of voice mail hell, and it’s just as frustrating.

Popular enterprise IM programs include IBM’s Lotus Workplace Messaging (http://www.lotus.com/workplacemessaging) and Sun’s Java System Instant Messaging (http://www.sun.com/software/products/instant_messaging). Companies offering IM gateway programs that enhance the functionality of free IM clients such as AOL Instant Messenger, Yahoo! Messenger, and MSN Messenger include Akonix Systems, Inc. (http://www.akonix.com), FaceTime Communications, Inc. (http://www.facetime.com), and IMlogic, Inc. (http://www.imlogic.com).

The bottom line is this: You need to use the medium that will best serve your purposes. “IM isn’t like e-mail,” says Carton. “It’s completely different.”

Consider yourself warned.