If you are dealing with a blocked sink, then there are a number of ways that you can fix it. Here are a few methods to help you get through the process with ease.
Step 1 - Try a Plunger
The first thing that you want to try if you have a blocked sink is a plunger. You will want to put an old wet rag in the over flow drain if you are working in a bathroom to prevent suction or if you are in a kitchen with two separate drains then you will need to place a rag in the other. Place the plunger over the drain and then with an upwards motion try to clear the drain using the plunger. If you are consistent with the motions, the plunger will work for you most of the time and you will not have to move on to another technique.
Step 2 - Chemical Remover
If the plunger does not work then you can use a chemical drain opener to see if it will move the blockage through or break it up. All you need to do is follow the directions on the back of the liquid container and let it sit for the allotted time. Then once it sits you should see the level going down and you will want to run hot water through to flush it out.
Step 3 - Snaking the Drain
If neither the plunger nor the chemicals worked then you will need to move on to the next technique. Under the sink you can see a clean out plug that is near the lowest dip in the drain pipe. If you do not have a clean out plug then you probably have a drain that screws on and you will need a wrench to remove it if it is on tightly. You will also need a wrench when you are removing the drain plug. Place a bucket under the area so that when you open them you can catch any water that may come out. Once you have taken off the drain trap or the plug you can use a plumbers snake to move in and out ,trying to break up whatever may be stuck or blocking the sink from draining. While you are doing this make sure that a bucket is under the opening at all times as freeing up the drain may lead to a movement of water or whatever was trapped above. If you have a drain trap you will need to rinse it out with hot water. Once you have snaked the drain pipe and rinsed it out with hot water you can use the wrench to put everything back together. Hopefully this will help to remove the block.
These steps will almost always help you to remove a blocked sink however if you are still having problems after these three methods you should consider calling a plumber. Good luck!