Use a rubber band or steel wool between the screwdriver and screw head
Switch to a screwdriver or bit that fits more tightly
Tap a slightly larger flathead bit into the stripped head
Use locking pliers to grip the screw head if it is exposed
Cut a new slot in the head with a rotary tool or hacksaw
Apply a screw extractor kit
Drill a small pilot hole and use a left-hand drill bit
Drill out the screw head and remove the remaining shaft with pliers
Add penetrating oil if the screw is stuck
Heat the screw briefly to help loosen it
Replace the screw with a new one after removal