Remove any visible debris from the drain opening
Boil water and pour it slowly down the drain
Add baking soda, then vinegar, and let it sit
Flush the drain with hot water
Use a plunger over the drain opening
Seal any overflow holes before plunging
Remove and clean the sink stopper
Place a bucket under the P-trap
Unscrew the P-trap and clear any blockage
Reassemble the P-trap and test the sink
Use a drain snake or auger to break up the clog
Clean the drain snake after use
Avoid using chemical drain cleaners if possible
Repeat the process if the clog remains
Call a plumber if the clog does not clear