Question : House keeping

What should a user do to perform house keeping
i.e. disk cleanup?
eg defragmentation, save the least amount of files on the desktop, delete on / off line temporary files,
etc.?

Answer : House keeping

Basic Windows Housekeeping regimen I maintain is as follows and can vary from system to system:

IE Temporary files settings
tools\internet options\"browsing history" settings\  page I set the following:
Space for temp files - 150 - 200 MB - most systems that I view tend to have it set rather high
Also as a personal preference I create a temp file located on the root of the drive for ease of management of the temporary internet files folder.

Scandisk
I don't see the requirement to run scandisk too frequently however it is not a bad idea to run this tool periodically, I would say once every 2-3 months.  Others may recommend a higher frequency but this is definitely user preference.

choose "start>Run " in the run dialog type 'sfc /scannow'

Disk Cleanup
Run the disk cleanup periodically and you can automate this using the task scheduler.  The following link shows you how to automate this process using the task scheduler and the available switches for the application.  
http://support.microsoft.com/kb/315246