OK, now we’re going to talk nuts and bolts. Here are the steps you need to take to make viral marketing pull in big bucks and tons of customers.
Offer something that has value for free.

It has to have perceived value—you can’t just give away crap because no one wants crap. “Free” is the most powerful word in any marketer’s vocabulary. The most successful viral marketing programs give away valuable products or services to attract attention.

Think free e-mail service, free information, free buttons, free software programs that do awesome functions--but not as much as the “pro” version. One key point is that cheap things may generate interest, but “free” will get attention much faster.

Viral marketers are the high Zen masters of delayed gratification. They may not profit right now or tomorrow, but if they can generate a building-up of interest from giving stuff away, they know they’ll eventually make money. Free attracts eyeballs. Eyeballs then see other cool stuff that you sell and orders start rolling in. Eyeballs bring along e-mail addresses, ad revenue and sales. Here’s the rule: when you give away something, you sell something.
Exploit Emotions

Remember that people—even smart people online—are only human. Humans have emotions. Why did the “Netscape Now” buttons do so well when the web was young? Because people wanted be cool. Greed drives people.

People want to be popular, loved, and understood. And they love to communicate, which produces millions of websites and billions of e-mail messages. Design a marketing strategy that builds on common motivations and behaviors for its transmission, and you have a winner.

This is why sites with polls and user forums do so well.
Another facet is that you need to talk to the user like you understand what they’re going through—a little sympathy goes a long way!