Todd Hooper provides an overview of customer development and discusses three simple rules for startups. Customer development involves synchronizing product development with customer feedback to achieve problem/solution and product/market fit. It is the opposite of traditional product development. The key stages are customer discovery, validation, creation and company building. Three rules of customer development are to get out of the building, listen to customers first then talk, and test hypotheses by building for a few passionate customers rather than many indifferent ones.