Turn off the water supply to the bathtub
Plug the drain to prevent losing small parts
Remove the faucet handle
Take out the escutcheon or trim plate if needed
Inspect the cartridge, stem, washer, O-ring, and valve seat
Replace any worn, cracked, or damaged parts
Clean mineral buildup from the faucet components
Reassemble the faucet
Turn the water back on
Test the faucet for leaks
Replace the entire faucet or call a plumber if the leak continues