This document provides a quick guide to the customer development process for B2B startups. It describes the four steps as discovery, validation, creation, and building a company. In discovery, founders do research, test assumptions about customers and problems, and meet with potential customers. Validation involves creating sales tools, selling to "rebel" customers, and verifying the product and business model work. After validation, startups have a proven product and sales process and can raise funds to enter the creation and building a company phases. The guide emphasizes continuously testing assumptions and adapting based on customer feedback.