Advertising is a huge part of any interactive marketer's budget. Banner, search, video, and mobile ads cost a bundle to purchase.

But expensive "paid media" is becoming less effective as consumers turn their back on ads that blatantly try to "sell" them something. (A recent Deloitte & Touche study found that three-quarters of US consumers consider Internet ads intrusive, and more than one-quarter would be willing to pay for advertisement-free online content.)

The good news is that a new marketing category—"earned media"—is emerging. It costs next to nothing and has an increasingly powerful impact on branding, consumer engagement, and return on investment (ROI).

Unlike paid media, which, as its name suggests, requires a significant financial investment, earned media is generated by the news, tweets, blogs, videos, and more that companies create for free.

In today's socially connected Web, people pass along informative, entertaining, and useful brand content through email, blogs, and social platforms such as Facebook, YouTube, and Twitter—spreading a brand's message authentically and driving valuable traffic to its websites and paid campaigns.

The main problem with earned media is that it has been difficult to measure and track its effect on traffic volumes, engagement, and conversion. But several new inexpensive tools are now available that allow marketers to accurately track the effect that passed-along links and word of mouth have on a campaign's overall ROI.

In our research that tracked the flow of shared content for brands, we found some eye-opening data: namely, 20% of unique visitors arriving at a brand's websites or landing pages come directly from shared links.

In short, when people share your branded content via email, social networks, mobile messaging, etc., the passed-along links drive one out of every five visitors to your site.

And, even more important, that traffic is of very high quality. Visitors who come to sites or campaigns from a shared link convert one-and-a-half to four times more often than those who come from other sources, including paid advertisements.

However, an effective earned-media program is not without challenges. To get people to share your content, it has to be compelling. And to find out whether it's working, you need to measure your earned-media program with the same metrics and precision that you apply to your paid-media programs.

Want to get started with an effective earned-media marketing program? Here are three tips for launching, measuring, and monetizing a low-cost earned-media program that will drive a surge in online word-of-mouth traffic about your brand.

1. Make your content king

The first step to creating an earned-media strategy is to create content that people will want to pass along. Work with your creative team or agency to develop entertaining, informative, or useful content that draws in and engages potential customers.

The content you create should entertain, with only a subtle hint about your brand. Videos, games, and contests work well. Or create content that gives consumers something in return for engaging with it: Offer a coupon, a prize, or a promotion if they provide their email address or click through to your site to sign up for a newsletter; that information is valuable for your future marketing efforts.

2. Start spreading the news

Once you've created your sites, videos, news, contests, games, or other content, you need to make sure they get passed along by your strongest brand advocates and by as many other people as possible.

Sharing happens virally, but it doesn't hurt to give it a push!

Seed your videos to YouTube, post links to your contest sites on your Facebook page, bookmark and "tweet" about your new game site or branded entertainment campaign.

And don't forget to include a "share" link or button on every component of your earned-media campaign—on websites, via your tweets, in email messages to your subscriber base, embedded at the end of videos, etc.

Seed your content to blogs and forums where people discuss your brand; find those places by using a social-media monitoring tool that shows where word-of-mouth conversations are taking place about your brand; but always be transparent about who you are and don't be overtly "salesy."

3. Measure, monitor, and monetize

Earned media may spread on its own, but you still need to carefully and continually measure the program's effectiveness. Make sure to use a social-media monitoring and word-of-mouth measurement tool to find out exactly who is sharing your content and on which sites they are sharing it, and how much traffic that pass-along activity is driving to your website or campaign sites.

There are lots of "listening" tools out there, but you need to do more than get a general view of your marketing "buzz." You need to find out where your links are being placed and how such link-sharing is driving traffic.

Is YouTube driving more pass-alongs of your videos than your outbound email campaign that has embedded links to your videos? Is email the way that most people are passing on the link to your contest website? Are there certain blogs where people are talking about and sharing your content? Is Twitter or Facebook driving the most traffic to your site from shared links? Have text messages played a role in passing along links?

When you get an accurate reading of where, how, and with whom your content is being shared, you can make strategic decisions about both your earned-media and paid-media programs.

Knowing which content drives the most sharing helps you jettison the less-popular content and create more of the content people want; and knowing which sites drive the most sharing traffic allows you to make strategic paid-media buys on those sites or fine-tune your keyword-buying strategy to capitalize on real-time buzz.

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Remember, you can buy as many banner ads or paid search ads as your budget allows—but when people share your message for you, that has a much bigger impact on branding and sales than paid ads alone.

Ben Straley is CEO of Meteor Solutions (www.meteorsolutions.com), provider of a word-of-mouth analytics and optimization platform that enables marketers to measure, manage, and monetize earned media.