I practice various methods to auto clean my disk which I'm mentioning here. Hope this helps.
1.Use Disk Usage Analyzer by going to Applications->Accessories->Disk Usage Analyzer and click on the Scan Filesystem at the top to get it to analyze your disk usage pattern.
Now u can easily analyze which files are waste and its time to trash them.
2.Clean up your package installation using the following commands.
clearing up of the partial packages:
sudo apt-get autoclean
clearing up of the apt-cache :
sudo apt-get clean
cleaning up of any unused dependencies:
sudo apt-get autoremove
A good practice to avoid any left behind is to use the autoremove command whenever you want to uninstall an application.
sudo apt-get autoremove application-name
3.Use Computer Janitor by going in Administration->Computer Janitor. It automatically scan and displays all the unused packages which can easily be deleted. But be careful it also shows the .deb packages installed manually(i.e. not using apt-get).
And I'd suggest u to check out this page for more advanced techniques..
Hope that was useful.