Whether you run a small, part-time business out of your home or are part of a multinational corporation, tapping into the power of the Internet can help generate sales. It can also backfire, if you don’t respect Internet conventions and human decency.

Like the Internet in general, what most distinguishes Internet marketing is its interactivity. Unlike traditional advertising, which is one-way from advertiser to target market, Internet advertising is two-way. Prospects and customers can, and do, talk back to advertisers, and they talk among themselves.

“Internet marketing is word-of-mouth advertising on steroids. It invites users to take control, to create their own messages and share them,” said Dave Evans, co-founder of Digital Voodoo (http://www.digital-voodoo.com), a marketing technology consultancy in Austin, Texas. Evans specializes in what he describes as “social media.”

Social media encompasses older Internet offerings such as e-mail discussion lists, Usenet newsgroups, Web communities, and product review sites as well as newer offerings such as blogs, wikis, and podcasts.

The key difference between these Internet advertising media and traditional advertising media is that the later is interruptive (advertisers stop you from doing what you were doing to bring you their message) while the former is participative (advertisers can join in with whatever you’re doing). Evans recommends to his clients that they participate.

“You need to get the support of vocal user communities through which individuals can credibly spread the word about your products or services,” said Evans. In the Internet age, “to truly persuade, you must engage.”

Evans acknowledged that you can’t engage people within a social network without disturbing the network itself. In doing that, if you’re not careful, you can wind up coming across as manipulative.

The classic case of manipulative new media marketing that backfired involved Sony Ericsson. When it launched a new camera/cell phone in 2002, it hired actors to pretend they were foreign tourists in New York City. To help spread the word about the new gadgets, the actors, fake accents and all, asked New Yorkers to take a picture of them with the device.

After the truth surfaced, people were indignant. The backlash became larger than the campaign itself, and the brand took a knock. If you do a Google search today for Sony Ericcson and actors, you can still see the indignation.

Though the Internet didn’t play a direct role here, it does make it easy for individuals and companies alike to mask their identities. Avoid the temptation. Given the connected nature of consumers today, it’s typically just a matter of time before any disguised marketing effort will be widely exposed. Truth reveals itself.

“Be 110 percent transparent,” recommended Evans. “Tell people who you are, what you’re selling, and why you’re trying to sell it to them.”

The classic way to market products or services through participative technologies is to establish yourself as an expert and provide objective content that goes beyond your specific products or services. To sell, you first have to be useful. The more useful you are, the more you’ll persuade people to visit your Web site and to check into your products or services.

This advice still applies today with broadband and iPods. You need to find out who your core talkers are and where they’re talking. Give them positive subjects to discuss, track what they’re saying, and determine how this affects your overall marketing efforts. If you do it right, consumers will advertise for you.

As an example, said Evans, say you’re in the travel business. One effective new media marketing technique is to create your own travel blog and participate in the travel-related blogs of others. But don’t just blog about your product or service. Give people useful information about topics such as traveling with children.

No matter where you try to market yourself online, don’t just leave a hit-and-run ad. You have to schmooze. Join in or start useful, friendly conversations that give you an opportunity to eventually discuss what you’re trying to sell.

To direct people to your Web site in a nonannoying way, you can include its address, as well as other contact information about you, in your sig file. That’s the short “signature” that many e-mail and Usenet programs and Web sites let you automatically append to the end of your messages.

At HearThis.com (http://www.hearthis.com), a part of Evans’ Digital Voodoo marketing consulting business, you can listen to 28 10-minute podcasts on word-of-mouth advertising for free.