* Under the sink you will find a J-trap. Both sinks flow into this J-trap before the water goes out into the sewer line.
* Put a pan or bucket under the trap. Loosen the nut on either end of the trap and slide the trap out. Clean it out.
* At this point you should be able to tell whether the trap was clogged of the line to the sewer is clogged.
* If the sewer is clogged, push a snake into the pipe. Rotate the snake while you're pushing into and out of the pipe.
* If this doesn't do it, call a plumber.
* Good luck... Adios... Jasper...