The goal of attempting to diagnose the problems should be to eliminate components known to be working and isolate the problem to one area. Write down information such as how much memory is on the machine, number of SCSI controllers, periphereals, etc. If your machine is being set up by a technician, watch the technician set up the machine and ask questions. Verify the fan is running or that the LED is lit. If the circuit has power then the power supply on the machine has probably gone up.
Many systems have a power-on self test.
That self test will check the components of the system and usually give some indication of what failed. This is usually done by specifying test 2 failed, and then you look up what test 2 was in the hardware manual for your machine. Verify the disk is powered up, usually this can be done by listening for the fan. Does this happen, if not then you may have a bad disk. Booting up off an alternate root partition on a different disk may allow you to test this.