This one isn't too hard. Although one genius kid I know had to be walked through it (which is odd since he gets most others correct immediately).
There are three sock drawers in a dresser. The drawers are labeled as white, black, and mixed. Every drawer is labeled incorrectly. One drawer contains all white socks, one all black socks, and one has a mixture of white and black socks. You are allowed to close your eyes and pick one sock from one drawer. How can you correctly label each drawer?