Unclog your Sink
Once a clog has formed, preventive measures will not work. It is time to get out the plunger. Partially fill the sink with water to cover the plunger head. If you have a double sink or an overflow opening, stuff a wet rag into the second drain or opening. This will focus the plunging pressure on the clog.
Now plunge up and down vigorously, keeping the plunger sealed against the bottom of the sink. If you do not feel the water swishing back and forth or enough resistance, then air may be escaping through the second drain or overflow opening. Have a helper hold the wet rag firmly in place.
Once you have broken the clog loose, run hot water through the drain to flush out the debris. If the clog is too stubborn for the plunger, it is time to try the drain auger. Generally you have 2 choices when using the auger.
You can go in through the drain or you can remove the trap and go into the horizontal drain line. Use your judgment based on where you think the clog is located. You can remove the trap using large channel locks or a pipe wrench. Wrap a rag around the area you are clamping onto. This will prevent the teeth of the tool from marring the pipe surface. Remove the two nuts that hold the trap. You need direct access into the horizontal stretch of pipe. Be sure to put a bucket under the trap to catch the water contained in the trap.
The most suitable auger is a coiled cable that wraps inside a housing. The housing should have a handle and a crank on it for spinning the cable inside the drain. Using a sensitive touch, feed the cable into the drain or horizontal pipe. When you feel some resistance, you are probably up against your clog. Pull an extra 18 inches of cable out of the housing, tighten the setscrew securing the cable, and turn the crank on the auger applying moderate force so that you push the cable into the drain or pipe. When the free cable has worked its way into the pipe, loosen the setscrew and pull out another 18 inches.
Continue this procedure until the cable has reached the larger vertical pipe. Pull the cable back out, cleaning it and feeding it back into the housing as you go. If you removed the trap, replace it now. The nuts holding the drain in place should be put on hand tight and then turned about a quarter turn with the wrench or channel locks. Do not over tighten. Once the trap is replaced, run hot water through the drain to flush it out. If water backs up, there may still be some loose debris in the line left behind by the auger. Try plunging to get rid of this debris. Again, flush the drain with hot water. If none of this works you should contact a local plumbers.