First, install two packages; localepurge and deborphan, both can be found in the Ubuntu repos.

Now we are ready to begin!

Getting rid of Residual Config packages

In Synaptic, on the far left hand side, you may see a category called "Residual config". Click on it, remove all the packages in that section. These are all the old packages which you had installed, which have left parts of the old package behind, this will now clean it up.

Getting rid of partial packages

In the terminal type:

sudo apt-get autoclean

This will remove partially completed packages, which I not needed.

Getting rid of unnecessary locale data

You have justed installed localepurge, this will run everytime you install or remove packages from Ubuntu. It will make sure there are no unused locale files or man pages left on your computer after the package was removed. You dont need to worry about this tool, it will work all by itself.

Getting rid of orphaned packages

In the terminal run this command:

sudo deborphan | xargs sudo apt-get -y remove --purge

When you remove an application from your computer, it may leave behind alot of unnecessary libs and other tools for that application to run. These are not needed now, this command will make sure there are no unused packages.

Thats it! Your computer should have more space free now! A more cleaner and slim-lined computer. Make sure you run these commands every so often, so your computer is always clean!