Napolean has secret meetings to help assert his control over the farm. After Snowball leaves, he decides that the meetings will be private and he will preside over them. This helps ensure that the other animals do not know what is going on and prevents them from protesting. Napolean has more control, therefore, because individuals will not speak up. These private meetings also help to give Napolean a "clean image", so the other animals will be more likely to trust him. He also does this by not talking to the animals.