Pull on a pair of rubber gloves to protect your hands. The gunk that comes out of the drain will be full of germs and chemicals.
Remove the stopper if your sink or bathtub has one. Depending on the brand of fixture, the stopper comes out differently.
Remove any hair or debris on the stopper and throw the gunk into the trash. Do not throw it into the toilet or you risk plugging the toilet drain.
Fill a 1-gallon bucket with hot water and a few drops of dish-washing soap. Wash the stopper in the soapy water.
Remove any hair or other debris that may be caught in the crosshairs of the drain. Tweezers or needle-nosed pliers can pick the gunk out if you don't want to use your fingers. Throw the gunk away into the trash. If this does not solve the problem, proceed to the next step.
Apply a thin layer of petroleum jelly over the lip of a plunger.
Place the plunger over the drain and fill the sink or tub with hot water. You'll want enough hot water to cover the rubber portion of the plunger.
Plunge the drain in quick up and down movements. Repeat steps 6, 7 and 8 several times if necessary.
Pour 1/2 cup of baking soda into the drain.
Add 1/2 cup white vinegar into the drain. The foaming action will clear out remaining debris in your drain.
Allow the baking soda and vinegar to stay in the drain for three hours. Do not use the drain during this time.
Bring a tea kettle or pot of water to a rolling boil on the stove.
Pour the boiling hot water into the drain.
Turn on the hot water and continue to run hot water down the drain for another five minutes.