Start with chilled eggs, since they're easier to separate without breaking the yolks. Gently crack the egg, keeping the shell together. Hold a cupped hand over a bowl. With the other, gently separate the shell along the crack, letting the yolk and white drip into your waiting hand. Keeping the solid yolk in your hand, allow the white to fall through your fingers into the bowl below. Fat, which is found in yolks, is the enemy of light, airy, stiffly beaten egg whites. Reserve the yolk in a separate bowl for another use, and throw away the shell.