Turn off the water supply to the shower
Open the shower valve to release any remaining pressure
Remove the handle screw and take off the handle
Remove the escutcheon plate or trim cover
Unscrew and remove the retaining clip or retaining nut
Pull the cartridge straight out with pliers or a cartridge puller
Wiggle the cartridge gently if it is stuck
Apply penetrating oil if needed
Use the correct cartridge puller for stubborn cartridges
Inspect the valve body for debris or damage
Keep track of all parts for reassembly