Plumbing

Balt, have you tried plunger yet

One of the simplest ways to clear a clogged bathroom drain is to use a plunger. Just place the rubber cap of the plunger over the drain opening, ensuring that the opening is entirely covered, and dispense a number of sharp downward thrusts.
Creating a series of compressed air blasts in this way often dislodges the offending blockage. If you are working on your sink, make sure you block the overflow outlet first. If left open the outlet will allow the compressed air to escape rather than exert pressure on whatever is clogging the pipe.

You can also try a product like Drano. And you might have to invest in a "snake" which is actually handy to have around for stopped-drain problems.

Where exactly is your problem? Sink, shower/tub or toilet?

Bing, I should add, plunging down entails the danger of a pressure surge if not disconnecting the plumbing down the line somewhere at least forcing the clog further down that way where it can reassert itself. So plunge down easy but up fast

First, place an empty bucket underneath the U-shaped pipe (the trap) beneath the sink. The bucket will collect the water that will spill. Using a plumber's wrench, loosen the slip nuts at both ends of the pipe. You should be able to finish the operation by hand. When the trap is free, remove it and turn it upside down, emptying the contents into the bucket. You may also need to fish around inside it for debris, and do the same with the pipes that were holding it. An old toothbrush is good for getting the tough gunk out. Rinse the trap with water and then put it all back together. In most cases, that will have done the trick.

Here a few ways to help you remove drain clogs and prevent them from forming in the future. Boiling hot waterTry attacking your clog with boiling water. Hot water won't do it — boiling is the key to dissolving any organic matter in your sink.