When making a meringue, always use egg whites at room temperature. You will get greater volume than if they are cold. If you’re using an electric mixer to whip your egg whites, finish the process by beating by hand for a more even texture. When combining eggs and sugar, mix them immediately. Don’t leave them uncombined in the same bowl or the sugar will 'burn' the eggs and create lumps in the mixture.
Source: Lara Cory