Hi Sandra,
I'm visiting WDW in December too and am hoping I get all the dining reservations I want!
I would advise you to go to
www.pscalculator.net and use the calculator there to tell you when you will be exactly 90 days prior to your trip, for example if you are arriving on December 10th then you can call on September 11th. If you will be staying at a WDW Resort then you will also be able to make the first 10 days of your dining reservations on that day too. Reservations can now be made in 2 ways either by calling 407-939-3463, lines open at 7am EST, or online via the dining pages of
www.disneyworld.com from 6am EST. For the reservations you want I would strongly advise you to be online at 6am, book Cinderella's Royal Table first as this is the most popular of your choices followed by Chef Mickey's, Akershus, Crystal Palace and finally 1900 Park Fare. I would then suggest you have your phone ready incase you were unsuccessful, also try and be as flexible as possible with your dining times, especially for the Castle. For example if you ask for an 8am breakfast you may be told there is no availability but if you ask for 8.15am there will be an opening. Have a little play with the online system, without actually booking anything, a few days before so you know how the system works.
Fingers crossed we both get all the reservations we want,
Jo