Turn off the water supply under the sink
Open the faucet to drain remaining water
Plug the drain to prevent losing small parts
Remove the faucet handle
Take out the cartridge, stem, or valve assembly
Inspect washers, O-rings, seals, and cartridges for wear or damage
Replace any worn or damaged parts
Clean mineral buildup from faucet components
Reassemble the faucet
Turn the water supply back on
Test for leaks
Tighten connections if needed
Replace the entire faucet if parts are unavailable or damage is severe