Temporary files

Clear tmp directory

$ rm -rf /tmp/*

Delete cache

On macOS:

$ rm -rf ~/Library/Caches/*

On macOS and Linux:

$ rm -rf ~/.cache/*

Remove thumbnails

$ du -sh ~/.cache/thumbnails
818M    /home/michael/.cache/thumbnails

$ rm -rf ~/.cache/thumbnails/*

APT

For Debian/Ubuntu.

Remove cache

Essential Guide: 5 Simple Ways To Free Up Space on Ubuntu

$ sudo apt-get clean

Check size of archives. This dropped to 184K after running clean above.

$ sudo du -sh /var/cache/apt/archives
1.8G    /var/cache/apt/archives

Remove unused packages

$ sudo apt-get autoremove

Remove packages by name

$ sudo apt-get remove package-name1 package-name2