1. Boil water on kettle or stove. Meanwhile, measure out the baking soda and vinegar into 2 separate containers.
2. Carefully pour contents of the container with the soda in it down the drain.
3. Assure that all of the baking soda is in the drain before pouring in the measured vinegar. Allow the foam from the drain to settle before pouring the boiling water down the drain.
If this doesn't work, try a plunger afterwards. Another great tip is if you wish, you may take the oily side of a citrus peel (orange, lime, lemon, whatever) and scrub your sink clean with the remaining baking soda and vinegar before pouring the water down the drain. The mix of the citrus oil and baking soda leaves the sink sparkling!
This works when your drain is clogged, but does not have water in the basin. A good plunger will help get rid of the water if necessary, and then you should use this wonderfully easy home cleaning solution to finish de-clogging! This is done by a chemical reaction, which produces heat and expands, so you should always wear safety goggles (remember those volcanoes you made for science class when you were young?)!'