Samuel Taylor (yes, that Samuel Taylor) shared a few things that works for him when joining a team and learning the codebase.

I have switched teams more often than I have had to implement an AVL tree, and you can guess which one of those two was taught in school. I wish someone had taught me how to join a new team! While learning a new codebase can be daunting, I’ve found a few things that work for me. You should do at least three things when joining a new team. The order of these three can be whatever you like, but all three should be done as soon as reasonably possible.