The increasing popularity of Web 2.0 tools, such as blogs, wikis, and virtual worlds, is fundamentally changing how consumers use the Web. The basic core of Web 2.0, that users can generate and share their own content, often regarding company brands and products, provides both potential value and challenges to marketing practitioners. Along with conducting secondary research, we interviewed 30 marketing executives and senior managers at companies at the forefront of using this technology. We found that there were four principles which guided managers' marketing actions: 1) facilitate users in generating content, 2) focus on building a community, 3) ensure authenticity of the message, and 4) look for marketing opportunities through experimentation.