A clog is a common problem that does not always require professional help. There are several drain clearing techniques you can try in order to remove the clog yourself. First, try plunging the drain. You can fill a sink partially with water and then use a small plunger to try to release the clog. For a double sink, stuff a wet rag into the opening of the drain that is not clogged while plunging the other one.
You can also clear a clogged drain with a cable auger. Go under the sink and use a pipe wrench to remove the sink trap, which is where many clogs form. If that is not where the clog is, insert the auger into the piping slowly until you feel resistance. You can then crank the handle slowly to break through the blockage.