A meringue is simply a mixture of beaten egg whites and sugar, often stabilized with an acid, such as cream of tartar or lemon juice. A soft meringue begins to sag shortly after it's made, so it is usually cooked on the top of a pie or folded into a batter.
To make a simple meringue, separate the eggs scrupulously. A little bit of egg yolk in the mix and your whites won't whip up as well. Also, let the whites reach room temperature, at which point they have less surface tension and will form bubbles more easily. The whites of older eggs whip better, because they are thinner, but the whites from newer eggs have more stability when whipped.
If you have an unlined copper bowl for beating egg whites, use it. The copper reacts with the whites and provides a loftier result. Don't use an aluminum bowl, which will react with the acid and turn your whites gray. A glass or metal bowl is better than plastic, as plastic may harbor traces of oil, which are fatal to a good meringue.
In a medium bowl, beat three eggs either with an electric mixer or by hand. Add 1/4 teaspoon cream of tartar and a pinch of salt. Begin beating slowly at first, which will produce small, stable bubbles. After a minute or so, increase the speed and beat until soft peaks form. Beat in 2/3-cup of superfine sugar, 1 or 2 tablespoons at a time until stiff peaks form, which will take 7 to 10 minutes. If you don't have superfine sugar, make your own by grinding granulated sugar in a food processor until very fine. This will make about 4 cups of meringue.