Other than the many great answers here I will frequently start by doing cleanups of the codebase. I'll start reading the files using any of the strategies ment

Other than the many great answers here I will frequently start by doing cleanups of the codebase. I'll start reading the files using any of the strategies mentioned here and looking for things I can cleanup. Formatting, Simple Refactors, Normalizing Names. These are all things that are comparatively easy to do and safe but force you to reason about the code you are reading. Asking yourself what you can refactor or fix the naming for is a deent forcing function for actually understanding the code.