List of files/folders writable by the web server?

Question

New to WP. I soon realized there are some files that need to be writable by the web server, otherwise various operations fail. Moreover, the lists seem to be different for different tasks. Not sure I'm in love with the concept, but okay, I'll work with it.

The trouble is, I can't figure out a simple way to determine which files / folders could be written to by the web server during the course of various actions. The documentation I've found seems either geared towards less technically-abled users ("just enable everything!") or focused on very narrow aspects.

Does anybody have the minimal lists of writable files for various operations, such as: uploading content, installing a plugin or a theme, upgrading WP (this one is easy: everything needs to be writable), etc.

Thanks!