Clean Up Disk Space
Settings
Use the path Settings -> General -> Storage -> Storage settings to find out how disk space is occupied and delete unnecessary files.
Find Large Files
Use du to find large files. For example, use the command du -hL -d 1 | sort -h.
In some directory, use find . -type f -print0 | xargs -0 du -h | sort -rh | head -n 20.
Delete Applications
Delete applications in the application directory.
Downloads
Remove downloaded package dmg files, which can be easily downloaded from the internet.
Portable Disk
Purchase a portable disk and move some files there.
iPhone
Import photos to your Mac and delete them after importing.