It would depend on where you are and what the airline policy is. I should imagine it is commonplace to have a competent person in the flight deck or on the ground supervising fuelling. Additionally the refuelling zone should be kept clear, seatbelts signs off, crew and pax aware, exits clear where there is no air bridge or steps attached to said door, and during disembarkation electronic devices should be restricted when walking to the terminal from the aircraft if the route goes near the refuelling zone. Some countries and airports don't allow it. Any airport specific procedures will be listed in the aip or company manual/airfield briefs. I hope this helps.