The default Debian installation puts lots of documentation with various locale on /usr. These files are not used most of the time but end up eating lot of disk space.
Debian provides localepurge and deborphan to remove unwanted files from hard disk and to retain disk space.
# aptitude install localepurge deborphan
Configuration of localepurge
# dpkg-reconfigure localepurge
Cleanup disk space
Following command finds unwanted and independent packages, which are no longer required and removes them
When packages are installed using online Debian repository, APT downloads them and stores all .deb files in /var/cache/apt/archives/. After the installation, generally these files are no more required. Following command cleans up these unwanted files and reclaims disk space.
# aptitude clean