Boil water and pour it slowly down the drain
Remove and clean the drain stopper or strainer
Use a plunger to dislodge the clog
Pour baking soda into the drain
Add vinegar and let it sit for several minutes
Flush the drain with hot water
Use a drain snake or auger to remove the blockage
Remove and clean the P-trap under the sink
Check for and clear any visible debris in the drain opening
Repeat the process if needed
Call a plumber if the clog does not clear