Don’t open the oven door when baking, instead, turn on the light in the oven to see what’s happening inside.
Use an food-safe thermometer to check doneness, the internal temperature should reach 160.
Don’t over beat the egg whites. For soufflés, we want soft-peak egg whites. When you take out your whip from the egg whites, the peak should fold over and the egg whites will still look very wet. They will not hold their shape. If you have gotten to the meringue-stage in egg whites, you have gone too far.
When folding in the egg whites to the soufflé base, make sure there are no egg white streaks. Although you want to do this step gently, don’t under do it. You will know that you have mixed it well, when there are no white streaks and no soufflé streaks, there is only one color: the combined mixture.
Use only straight-sided ramekins. If the ramekins have fluted or diagonal sides, it will be harder for the soufflé to rise over the top of the ramekins.