What should you clean when cleaning an office?

I have just got a part time job cleaning some office space for a friend of mine. I have never done a cleaning job before (always office jobs and admin type jobs) and I don't know what I should be cleaning. Obviously, I know how to hoover and clean the washrooms and kitchen, etc, but should I clean desks, phones, computers, etc? If so, should I move stuff to clean them, or just leave everything alone in those areas?