Our company procedure:
Position lights - on ground, aircraft powered
Beacon - engine start, towing or maintenance activity with dangerous activity
Strobe lights - crossing runways and from the moment of runway alignment clearance before takeoff
However, I worked on the Fokker 50, and there it was procedure to never turn on any lights on ground when the engines are not running. Because the lights tend to get hot without the cool airstream around them, and service life went down otherwise.