Whenever disk space gets almost full, I like to use the following software to clean up (unnecessary) big files from my computers:
Windows
WinDirStat is a disk usage statistics viewer and cleanup tool for various versions of Microsoft Windows.
It’s user-friendly and open source.
Linux / macOS
ncdu:
Ncdu is a disk usage analyzer with an ncurses interface. It is designed to find space hogs on a remote server where you don’t have an entire graphical setup available, but it is a useful tool even on regular desktop systems. Ncdu aims to be fast, simple and easy to use, and should be able to run in any minimal POSIX-like environment with ncurses installed.
Naturally, the command line way™ prevails on Unix systems. It’s one installation command away from your favorite package manager. Usage:
% ncdu /