This document provides a concise guide of what not to do when starting a startup. It lists common mistakes that can slow progress, such as overengineering solutions, underestimating costs, and being too stubborn to pivot ideas that are not working. The author emphasizes the importance of building the minimum viable product quickly, having funding to cover costs, ignoring naysayers, and learning from both successes and failures. The overall message is that perseverance is key to eventual success in the competitive world of startups.