The document outlines 4 lessons learned from a company's first version of customer development. The lessons are: 1) Start simply with paper prototypes before building software; 2) Understand your product's most important attribute; 3) Customer development does not require a designer; and 4) It's okay if not everyone likes your idea. The overarching lesson is that the discovery phase should focus on learning from customers and iterating based on feedback, rather than perfect execution.