if you try the plunger and/or chemical drain opener and still clogged go to the local hardware store and get a plumer's snake (ok, insert corny joke here). You can buy a small one for around $20-30 bucks, they're easy to use and should take care of the problem. Other course of action is get some towels, bucket, and pipe wrench and take off the drain trap (curved pipe under sink) if you clog is there you can use about anything to dig the crap out.
If none of this works, call the plumber.