Empty the room of all furnishings, including anything hanging from the walls. Spread drop cloths over the floor.
Turn off the circuit breakers powering the lights and electrical outlets in the room as a safety precaution.
Set a ladder or stool in the room and put on safety glasses and a dust mask to protect your eyes and lungs.
Remove the molding from the walls near the ceiling with a pry bar and dispose of the trim or keep it to later reinstall it.
Punch a hole into the drywall ceiling in a corner of the room using a chisel and hammer.
Insert the blade of a reciprocating saw into the hole and saw across the ceiling near the wall from one end of the room to the other, periodically stopping to pull down loose sections of drywall.
Repeat Step 6 as necessary, sawing and pulling down the drywall ceiling. Once the beams are exposed and no drywall remains attached to the ceiling, unfasten any screws protruding from the beams with a screw gun. You can then raise the beams and install new drywall.