Separate the eggs while cold; but bring them to room temperature before using.
Some strains of chickens have been bred to lay eggs that are lower in cholesterol; quite often, those eggs will not whip as well as standard eggs.
For a dramatic presentation, plan to fill your baking dish with enough soufflé mixture to puff "over the top" while baking; butter a piece of parchment paper, foil, or wax paper and wrap around the dish to form an extended collar; secure with kitchen twine.
Make absolutely sure there is no oil residue in your mixing bown before whipping your egg whites; separate your eggs one by one in small bowls, and ensure that each egg white has absolutely no yolk in it. Oil of any kind will dramatically decrease the volume of your beaten egg whites.
It is better to select a baking dish that is too small and augment it with a collar as described above than a dish too large; the soufflé won't rise if it's spread out too thin.
The soufflé base may be prepared up to the point of beating the egg whites a day or two in advance of baking. It may be held, refrigerated; just bring it close to room temperature before proceeding.