I use Ubuntu on my Netbook, Acer Aspire One. It has only 8 GB SSD as storage.
The disk space is always tight there. That is why I install Lubuntu on it. Light and quick respond.
After a few months use and a few times update. The free space is even tight. I have to do something.
OK, I would like to introduce this ubuntu tool, Ubuntu Tweak. It has a built-in function, Janitor.