How do I fix a dripping faucet?

A dripping faucet is most often caused by a worn washer, O-ring, or cartridge. Start by shutting off the water supply under the sink. Disassemble the faucet handle and identify the type: compression, cartridge, ball, or ceramic disk. Replace the worn part with an identical replacement from a hardware store. Reassemble and test. Faucet repair kits are inexpensive and widely available for most common brands.