Spray penetrating oil on the bolt and let it soak
Clean debris from the bolt head and surrounding area
Use the correct size socket or bit and tap it on firmly
Try a manual impact driver or impact wrench
Clamp locking pliers tightly onto any exposed bolt head
Use a bolt extractor socket
Cut a new slot in the bolt head with a rotary tool and use a flathead screwdriver
Apply heat to the surrounding metal if appropriate
Tap the bolt head lightly to help break corrosion
Drill a small pilot hole into the bolt center
Use a left-hand drill bit to back the bolt out
Insert a screw extractor into the drilled hole and turn slowly
Drill the bolt head off if necessary
Remove the part and grip the remaining bolt shaft with locking pliers
Replace the bolt after removal