Priority Seating [reservations] can be made up to 60 days in advance for restaurants in the Disneyland Resort! All you need to do is call 714-781-DINE.
Character Dining is also available at several locations throughout the Disneyland® Resort, and again, all you would need to do is call 714-781-DINE to make your reservations. Below is a list of current locations which feature this service:
+ Disneyland® Park - "Minnie & Friends - Breakfast in the Park" at the Plaza Inn,
+ Disney's California Adventure® Park - "Ariel's Disney Princess Celebration" at Ariel's Grotto,
+ Disney's Grand Californian Hotel® & Spa - Chip 'n Dale Critter Breakfast at Storytellers Cafe,
+ Disneyland® Hotel - Goofy's Kitchen, and
+ Disney's Paradise Pier® Hotel - Lilo & Stitch Aloha Breakfast at Disney's PCH Grill.
More information here: http://disneyland.disney.go.com/characters/
Here is a link to some great information about the restaurants at Disneyland:
And another for California Adventure:
And one more for Downtown Disney:
Hope this helps!