SCEE sent out some advance notice of a PSN outage in Europe via the PlayStation forum. Maintenance is scheduled on the network Thursday, December 15 from 4pm GMT (11am EST) to 2am GMT (9pm EST).
No such announcement has been made for North America, but we can safely assume that the EU outage will coincide with network interruption here. Besides, the only “preparation” you have to do for such an event is not make ironclad plans to play online games or buy things from the PlayStation Store right then. If it turns out that the network doesn’t go offline, just sign in and play extemporaneously.
