- Meringue whips up best in a squeaky clean bowl in which there's no residual oil or fat left behind to disturb or deflate it. Thoroughly clean your mixing bowl and whisk attachment before you begin, and consider wiping them down with a splash of white vinegar.
Avoid letting any egg yolk—even a small amount—into meringue batter, which can also deflate it. I learned from Shirley O. Corriher's book BakeWise to use the three-bowl method to separate the eggs. Crack the egg and drop the white into one small bowl, and if the yolk didn't break, and the white is uncontaminated, transfer the white to the mixing bowl for beating. If it gets contaminated, save it for breakfast and start again.
Meringue deflates and won't stay crisp in humidity. So on significantly muggy days, either close the windows and put the air-conditioning on while you're beating, baking, and storing the meringue, or choose another dessert.
Standard granulated sugar will work in meringues, but I prefer a fine sugar which whips into egg whites easily. Consider using caster sugar, or grinding granulated sugar in a food processor until very fine.
Be careful not to overbeat the egg whites. This can rob too much of the moisture from the meringue, and it will not expand as much in the oven. If the egg whites start to look lumpy instead of glossy and smooth, they've been overbeaten.
Meringue expands slightly in the oven, so be sure to leave ample room between dollops and build the meringues more upward than outward.
Meringue has a tendency to crack, especially from shifts in temperature. (The good news is: it's delicious whether it is cracked or perfectly smooth.) Avoid an abrupt change in temperature by leaving the meringue in the oven to cool after it's baked.