I recommend you go to Guest Services or the City Hall the first thing in the morning and ask them what time and where specific characters will be. They usually have a list which may change from day to day with all those details.
Fab 5 - you can see Mickey and Minnie in Toontown in their houses and usually Goofy is out and about sometime during the day as well.
Pooh, Eyeore and Tigger (and possibly Piglet?) can be found in Critter Country, there is a little meet and greet type area that they are usually in. I haven't heard of Rabbit being out before though.
There is the Princess Fantasy Faire which has up to 3 of the following (rotates throughout the day) Snow White, Cinderella, Aurora, Mulan, Belle, Pocahontas, Jasmine, Tiana, Ariel.
Alice and the Mad Hatter are often on Main Street, they do a 'game' of musical chairs sometimes during the day but again, I'd check with the City Hall. Also, in the morning just as the park is opening and probably during the rest of the day there are a few characters that hang around Main Street
If you want to get a good range of characters, maybe try a character meal. I know the Minnie and Friends one usually has Captain Hook, Minnie, Fairy Godmother, Pooh, Tigger, Chip & Dale (but it can change)
I hope that helps but I'm sure there will be others who can post more detailed information
