Thank you for this gentle introduction, I hope more people will get comfortable with the shell.
But for cleanup tasks, I prefer to use the fantastic GUI utility called DaisyDisk (daisydiskapp.com).
If you want a free option you could use Disk Inventory X (derlien.com)
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.