For marketers, Web 2.0 offers a remarkable new opportunity to engage consumers.

If only they knew how to do it.

That's where this article aims to help. We interviewed more than 30 executives and managers in both large and small organizations that are at the forefront of experimenting with Web 2.0 tools. From those conversations and further research, we identified a set of emerging principles for marketing.

But first, a more basic question: What is Web 2.0, anyway? Essentially, it encompasses the set of tools that allow people to build social and business connections, share information and collaborate on projects online. That includes blogs, wikis, social-networking sites and other online communities, and virtual worlds.

Millions of people have become familiar with these tools through sites like Facebook, Wikipedia and Second Life, or by writing their own blogs. And a growing number of marketers are using Web 2.0 tools to collaborate with consumers on product development, service enhancement and promotion. But most companies still don't appear to be well versed in this area.

So here's a look at the principles we arrived at -- and how marketers can use them to get the best results.

Don't just talk at consumers -- work with them throughout the marketing process.

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Web 2.0 tools can be used to do what traditional advertising does: persuade consumers to buy a company's products or services. An executive can write a blog, for instance, that regularly talks up the company's goods. But that kind of approach misses the point of 2.0. Instead, companies should use these tools to get the consumers involved, inviting them to participate in marketing-related activities from product development to feedback to customer service.

How can you do that? A leading greeting-card and gift company that we spoke with is one of many that have set up an online community -- a site where it can talk to consumers and the consumers can talk to each other. The company solicits opinions on various aspects of greeting-card design and on ideas for gifts and their pricing. It also asks the consumers to talk about their lifestyles and even upload photos of themselves, so that it can better understand its market.

A marketing manager at the company says that, as a way to obtain consumer feedback and ideas for product development, the online community is much faster and cheaper than the traditional focus groups and surveys used in the past. The conversations consumers have with each other, he adds, result in "some of the most interesting insights," including gift ideas for specific occasions, such as a college graduation, and the prices consumers are willing to pay for different gifts.

Similarly, a large technology company uses several Web 2.0 tools to improve collaboration with both its business partners and consumers. Among other things, company employees have created wikis -- Web sites that allow users to add, delete and edit content -- to list answers to frequently asked questions about each product, and consumers have added significant contributions. For instance, within days of the release of a new piece of software by the company, consumers spotted a problem with it and posted a way for users to deal with it. They later proposed a way to fix the problem, which the company adopted. Having those solutions available so quickly showed customers that the company was on top of problems with its products.