Lesson 1: Read Before You Write
The biggest mistake new contributors make is jumping straight to code. The best contributors spend 80% of their time reading existing code, understanding patterns, and studying the project's conventions before writing a single line.
Lesson 2: Small PRs Win
A 50-line PR gets reviewed in hours. A 500-line PR sits for weeks. Break your work into small, focused pull requests that each do one thing well.
Lesson 3: Communication is Code
The PR description matters as much as the code itself. Explain the why, not just the what. Link to issues. Add screenshots for UI changes. Make the reviewer's job easy.
Lesson 4: Tests Are Not Optional
In open source, your code will run on machines you cannot access, in configurations you cannot predict. Tests are your safety net. Write them first, write them thoroughly.
Lesson 5: Ego Has No Place
Your code will be criticized. Your approach will be questioned. Your PR might be rejected. None of this is personal. The project is bigger than any individual contributor, and that is the beauty of it.