Start at the component level
A stack of equipment may have been assembled over many years. List each component separately: player, receiver, amplifier, speakers and remote. Record the full model markings before treating the stack as a single system.
Make a connection record
With equipment safely powered down, photograph the existing external connections before moving it. Label your notes with the printed port names. Appearance alone is not enough to establish cable, speaker or power compatibility; consult the exact manuals.
Keep a useful history
Note which components came together, which were added later and which observations came from a previous owner. A clear record is more useful than a confident guess about how a system was originally sold.