A whisk is a must. Its a great tool for whipping air into a liquid or egg whites. They come in different sizes and must be used vigorously. It often helps to turn the bowl on its side while whisking.

Tip to whisk up fabulous peaks of egg white:
First let the egg whites stand at room temperature for about an hour in a covered bowl.
Make sure your whisk is grease-free.
Put the egg whites in a deep stainless steel or glass bowl and whisk with a wire balloon whisk.
Use a circular action from the bottom of the bowl upwards to create the best volume.