Thank you for asking – this is definitely my favorite topic.
A buyer persona is a detailed profile of an example buyer that represents the real audience – an archetype of the target buyer. Marketers can use buyer personas to clarify the goals, concerns, preferences and decision process that are most relevant to their prospective customers. Imagine how effective marketers could be if we would all stop making stuff up and start aligning our messages and programs with the way real buyers think.
There are many templates available for buyer personas. Use whichever template you like, but make sure that the content you include represents deep insights -- non-obvious information that gives you a strategic advantage over your competitors. The Five Rings of Insight are detailed here, including tips and examples.
I certainly didn't invent the idea of buyer personas -- but I've worked with thousands of marketers on their development and application and am now a huge advocate.
Don't confuse buyer personas with user personas. Design engineers frequently build user personas as a part of their product development process. The application of personas for marketing is less common, but hardly without precedent. Presidents Bill Clinton and George W. Bush successfully campaigned to the soccer mom persona during the 1992, 1996 and 2000 elections. By 2004, the soccer mom had morphed into a security mom persona as school violence and terrorism became big issues. The Presidents' campaign staffs used dozens of personas like these to focus their messages and win more votes.
I hope that my use of political examples doesn't suggest that you need a huge budget for this to work. I know marketers in companies of every size who are building buyer persona profiles through informal methods that cost next to nothing. They started by seeing every on-line or in-person interaction with a potential buyer as an opportunity to listen and identify patterns. I started this blog so that I could communicate with marketers who are interested in using personas to think more strategically about how to go to market. I'll be talking about examples and practices that anyone can implement. Please contact me if you find something useful that I can include here.