If you're like many free agents, you've found that word of mouth is the most effective and cheapest way to draw new prospects to your business. But maybe passing out business cards and talking up your services isn't producing enough results. To supercharge the word of mouth effect, try a simple injection of viral marketing.

The Theory of Viral Marketing

Viral marketing is the buzz, but what exactly is it? Let's illustrate with the preeminent example of a product made famous by viral marketing: Hotmail. When a registered user sends a note with this free Web-based email service, an advertisement containing a link to Hotmail.com is automatically added to the end of the message. The user communicates the marketing message passively, simply by using the service. In this way, "each new user becomes a company salesperson, and the message spreads organically," write venture capitalists Steve Jurvetson and Tim Draper in their article "Viral Marketing."

Even if you have the spare cash to do so, "it is hard to spend your way to Hotmail-like growth" with traditional advertising and marketing, say the article's authors, who are managing directors at Draper Fisher Jurvetson in Redwood City, California. Hotmail has amazed industry observers by growing from zero subscribers to more than 65 million in about four years. Hurray for Hotmail and owner Microsoft Corporation, but how can you harness the power of viral marketing for your small business? Let's take a look at the possibilities, medium by medium.

Email Newsletters

Email may also be your ticket to accelerating the growth of your customer base. Marketing consultant Marcia Yudkin uses her free Marketing Minute email newsletter to keep in touch with prospects and clients. Because subscribers can effortlessly forward the weekly missive to interested friends and associates, "the newsletter certainly has brought me new clients out of nowhere," says Boston-based Yudkin. If the recipients are impressed by the content of the newsletter, they may call Yudkin to check out her marketing services.

T-Shirts

The marketing virus carrying the message of your business doesn't have to be communicated electronically. "If you give away a T-shirt that's branded, someone is promoting you by just wearing it," says Yudkin. And with a little ingenuity, you can amplify the viral spread of your message. For example, you could give away T-shirts on the first day of a trade show and then offer an extra incentive to anyone who wears the shirt on the show floor the following day.

Real Postcards and Virtual Greeting Cards

"Another example [of viral marketing] is motels that offer free postcards," Yudkin says. "In sending them out, you're promoting the motel to whoever receives the card." Similarly, Web sites such as Blue Mountain Arts (bluemountain.com) have used the lure of free electronic greeting cards to lure millions of visitors onto pages carrying paid ads. Want to reply in kind? Blue Mountain's happy to convert you from a recipient into a registered user by offering you dozens of virtual thank-you notes.

Bylines and Bios

Do you ever write for trade publications or Web sites in order to showcase your expertise? Take full advantage of the viral spread of your name to pass along readers by including your email address or URL in the byline or author's bio. Similarly, when you email a report to a client, be sure to add a "signature" to the body of the message that includes your tagline and contact information. Your contact will often forward your emailed report to other powerful people in the organization, which may in turn lead to new business for you.

Finally, don't forget that viral invasion is just the first step in the marketing process. As Jurvetson and Draper put it, "rapid growth is of no value without customer retention." So roll up your sleeves and infect those new prospects with the excitement of the full value you can add to their organizations.