1. Use Cold Eggs - We learned this tip from an issue of Saveur a while back, and it works like a charm. When they're cold, the yolks and eggs seem to hold their shape better and separate more easily. If the recipe calls for room temperature eggs, just separate them first and let them warm in separate bowls.
2. Crack Eggs Against the Counter - After trying lots of different egg-cracking methods, we find that hit the egg gently against the counter is the surest way to avoid jamming bits of shell into the interior and potentially breaking the yolk.
3. Use the Three-Bowl Method - When we know we're going to be separating several eggs, like for meringue or angel food cake, we set up three bowls at our work station. We crack the whole egg into the first bowl and use our fingers to gently lift the yolk free of the whites. The naked yolk goes into the second bowl and the left-behind egg white is poured into the third. The next egg is then cracked in the (now empty) first bowl and the process repeated.
This might sound tedious and like a lot of dirty dishes, but it's all worth it the one time a yolk breaks as you're cracking it. Instead of ruining the whole batch of egg whites, you've only lost one egg. If you prefer to separate your eggs by passing the yolk between the two egg shells, just do it over that first bowl and then transfer the white to its own bowl when you're done.
What other tips do you have for separating eggs?
Related: What to do with Leftover Egg Whites