Turn off the water supply
Open the shower taps to release remaining water
Cover the drain to catch small parts
Remove the tap handles
Remove the trim plates or escutcheons
Unscrew and remove the tap cartridges or valve components
Inspect the valve body and clean the area
Install the new cartridges or tap components
Refit the trim plates and tap handles
Turn the water supply back on
Check for leaks
Test hot and cold water flow and adjust if needed