SouthernGirl528:
DCL will post on their Facebook page when they announce their itineraries, something along the lines of "We are pleased to announce that DCL will be sailing to . . . " like for the summer 2016 itineraries they posted a video of Brent the cruise director announcing the itineraries. Once that announcement is made, Platinum and Gold can start booking the following day (not sure of time - 8am EST? not sure). Silver and others can book the day after that. In the past, it has typically been: announcement made on a Tuesday, so Platinum/Gold bookings Wednesday and others book Thursday. Based on past years, the best guess I heard is that the announcement will come next week for fall/winter 2016.
SpicyCrab: I have booked over the phone on opening day, because I wanted certain cabins, connecting cabins etc. There is typically a long wait on hold. There are typically posts on this board that morning about wait times, etc.