The methods used by the Nazis to ghettoize Jews varied from place to place. In some cases, they used force and violence, while in others they used deception and trickery. In some cases, they established ghettos gradually, over a period of months or even years, while in others they did it quickly and suddenly.
In general, the Nazis tried to keep the ghettoization of Jews as secret as possible, in order to avoid resistance and panic. However, news of the ghettoization often spread quickly, and there were many cases where Jews were able to escape or go into hiding before they were caught.