I use "sudo apt-get autoclean" and "sudo apt-get clean"
See details in Ubuntu help: <https://help.ubuntu.com/community/AptGetHowto>
apt-get autoclean - Run this periodically to clean out .deb archives
from packages which are no longer installed on the system. You can
regain lots of disk space that way. If you're really desperate for
disk space, apt-get clean is more radical, and will remove .deb files
even for packages currently installed. But most of the time you
probably don't need the .debs any more, so it might be worth it if
you're strapped for megabytes.
apt-get clean -- the same as above, except remove *all* packages from
the package cache. Usually you don't need them, so this is smart if
you're running low on disk space. If you're on dial-up, you might
reconsider.
* The package cache is in /var/cache/apt/archives, so "du -sh
/var/cache/apt/archives" will tell you how much space cached packages
are taking up.