The whole answer deserves a post (or maybe a book!) unto itself, so obviously most people get a really abridged version. But one important aspect is to making it work is to think about writing even when you're not actually writing.
So...if I have a two-year-old daughter currently obsessed with Disney princesses, I'm hardly going to overlook the opportunity this presents: plot analysis. You can learn a lot in unexpected
For example... The Little Mermaid has taken the title of favorite princess movie in unofficial polls for ages. After watching it over a dozen times now, along with the rest of the princess classics at least one or two times each, I'm beginning to develop a theory: even little kids get it. Better plots make better movies, period.
Here's my princess-by-princess analysis:
SNOW WHITE: Whole annoying voice thing aside, this girl does nothing for herself besides look pretty and maintain a sweet disposition. It's kind of pathetic that the villain(ess) has a more complex and intriguing personality than Snow White herself does. The queen's personality flaws provide the entire conflict, and the introduction of a random, cookie-cutter prince resolves everything.
CINDERELLA: No annoying voice...just plain annoying. Perhaps it is my overly-active mother-sense, but it seems to me as though Cinderella whines an awful lot for someone who is taking no action towards making her life better. And she's kind of, well, stupid. WHY does she run downstairs in her pretty pink dress the mice made for her and dare to ask her stepfamily: "Oh, isn't it beautiful?!" What did she think they were going to say? Then she moons around at the ball about how she's finally found her true love, only to leave him with no hope or means of ever seeing him again. Lucky for her, the prince, despite being boring in all other aspects, has the naive perseverance to try the shoe-fitting tactic...
SLEEPING BEAUTY: At least she met her prince once, even if she was a baby...but, face it, she spends the majority of her story (chronologically) sleeping. The story really belongs to her fairy godmothers, not her. They're the ones who make difficult choices, who make mistakes and learn from them, who actually grow as characters. Briar Rose, in the meantime, has a nice nap before waking up mid-smooch.
THE LITTLE MERMAID: Back onto this one... Finally, Ariel is a princess with a brain and free will and a plan for her life. She is a good person with a weakness that leads her to make a foolish decision, upon which the entire plot hinges. (Aristotle would be happy.) Everything that follows is likewise contingent upon either a decision she makes or someone taking advantage of her decisions.
Secondly, Ariel is a lovable character. She's not afraid to be a little silly, she's really passionate about life, and she gives her love whole-heartedly. As an added bonus, what a great guy is Eric? He's fun, cute, musically gifted, really nice to his servants, sweet with his dog--and to top it off, he risks his life to save Ariel without thinking twice about it.
BEAUTY AND THE BEAST: This one's pretty good (Belle was my favorite as a kid--probably because she loved books), but fails somewhat in believability. I don't mean the dancing spoons, either... Rather, both the Beast's change of heart and Belle's reciprocal love don't seem to have sufficient impetus. Somehow Disney makes it all happen throughout the course of one song, so even if it is supposed to take a while, we miss out on experiencing it. I have to admit, though, Gaston was a great addition to the original version.
ALADDIN: Although technically "Laddy" (as my two-year-old calls him), and not Jasmine, is the protagonist of this movie, it succeeds where earlier movies failed--or did not dare to tread. At long last, both guy and girl have real, developed personalities, problems, and conflicts. They really fall in love, and together they experience enough hardship that it's reasonable for the audience to believe their love will last past the end credits. There is one aggravating plot flaw, however: the Sultan just up and changes the marry-a-prince law at the very end... Why, exactly, was he so blind to this law in the first place if all it took to change was a word on his part?