In this first part about word of mouth marketing, I build upon the podcast with fundamental information about word of mouth. I offer some examples of how marketers have capitalized on the different types of word of mouth that we can distinguish. Then, I address the mechanisms that generate buzz or viral spread of information. In this part of the session, I address the influentials theory, i.e., the idea that some consumers are more likely to ignite buzz, and to influence people's behaviors and opinions than others.