You will get more volume when beating egg whites if you first bring them to room temperature by setting the eggs out on your counter at least 30 minutes.
The bowl has to be perfetly clean with no no greese or soap residus.
Do not incorporate all the granulated sugar at once but a tablesppon at the time and whisk well in between.
Stop when your egg whites have stiff peaks. If you overbeat them, they will liquify again.
Use whipped egg whites right away. Do not let them sit or they will collapse.