One thing that I have done is to look at a Web Site picking that cruise. Then looking at what categories are still left. Then drill down and see how cabins there are left in the categories.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08
Miracle almost always sails FULL. You may not get your cabin assignment until you get to the dock, but chances are excellent that you'll get some kind of an upgrade. Probably just a higher deck, and the same "type" cabin. You'll have a great time on the Miracle. Wish we could join you.