The technical section of this book won't go deep on any specific technology or language, nor will it be a holistic introduction to software engineering. Instead, I'll try to highlight the highest-leverage principles of coding, debugging, operations, and software design that I haven't seen well taught elsewhere; my emphasis will be what I consider important in practice in industry. I'll also share a large list of specific practical tools I think every software engineer should learn about, including the usages you should focus on. My goal is to help you focus some of your applied study for the best possible practical returns. While I'm a backend and kernel engineer by training, I've attempted to keep this section general to all specialities.