Phone storage is full again. What is actually worth keeping?

A phone can have thousands of screenshots and still somehow be missing the one receipt that matters. Clearing everything sounds simple until there are family videos, work documents, and six versions of the same photo mixed together. Then an app suggests paying for more storage, which only postpones the sorting. How do you keep this manageable without turning it into a weekend project? A small routine would probably beat a dramatic cleanup every few months. Share the boring system that actually sticks, including what you delete without thinking twice.