For very little money or effort, even the smallest online businesses can use viral marketing techniques -- the same techniques that helped make one of the largest online shopping destinations.

Amazon encouraged its customers to send books as gifts to their friends. The friends received an Amazon flier along with the book; it encouraged them to shop at the site, which helped drive new customers. Amazon also pioneered the affiliate program model, paying businesses commissions when Amazon banners, buttons, and links placed on their sites resulted in sales.

Why Viral?

Viral marketing is "network enhanced" word-of-mouth -- any marketing in which the customer becomes an advocate for the product or service by recommending or sending it to friends. It proliferates like a virus, often by e-mail.

What are the elements of a successful viral campaign?

It spreads itself -- you only put out a small initial effort. Attach your marketing message to a product or a service, and if customers like your product, they pass it -- and your message -- on. Viral marketing depends on customers' good experiences. If a company doesn't satisfy customers, they won't recommend its product.

It sells through existing communication networks. This can take the form of articles or press releases to get your message displayed on others' Web pages or e-zines. Or you can place your message into existing relationships between people.

Blue Mountain Arts employs these relationship networks by providing electronic greeting cards people can e-mail to friends and family. Recipients are invited to visit the site to send their own cards.

Viral tactics provide for effortless transfer among customers. A short marketing message attached to a free product or service works best. E-mail, graphics, and software downloads are ideal carriers. Hotmail struck gold with this strategy, including a brief note in every e-mail message: "Get your private, free e-mail at"