Stopper in downward position
First of all you need to put the stopper of your bathtub in the downward position. This is to guard small screws from falling into the drain.
Protecting the finish of the tub
In order to protect your tub from scratches, you can lay a sheet or few towels inside the tub.
Identify the type of head of bathtub spout
After taking precautions, you need to get in the tub and then look under the bathtub spout with help of flashlight. Seek an open slot where the spout is screwed to the plumbing pipes. After finding the set screw, you need to examine the head in order to find out which type of screw is used. It can be either Philips headed or hex headed.
Pull the bathtub spout away from the wall
Next you need to remove the bathtub spout form the wall. You can do this by turning the screws counter-clockwise. You will be required to use either a Phillips screwdriver or a hex wrench in order to turn the screws. For removing, turning clockwise for only two or three times will loosen the spout.
Apply masking tape
Bathtub spouts which do not have any set screws are threaded on house plumbing pipe. You need to attach the masking tape near the diverter stem in order to protect the bathtub finish.
Use a pipe wrench to unscrew the bathtub spout
First adjust the jaws of a pipe wrench on the bathtub spout and masking tape. Then use the wrench to turn bathtub spout counter-clockwise. When the spout is loosened, you can use your hand to remove the bathtub spout. Continue unscrewing the spout until you remove it from the plumbing pipe.