How can I fix a leaky double handle bathroom sink faucet?

To fix a leaky double handle bathroom sink faucet, you can start by turning off the water supply to the faucet. Then, remove the handles and the cartridge or stem inside the faucet. Check for any worn out or damaged parts, such as O-rings or washers, and replace them if necessary. Reassemble the faucet and turn the water supply back on to test for leaks.