So many of the classic fairytales are based on old legends and myths. The Brothers Grimm collected German ones. Hans Christen Andersen also collected (and embellished!) and of course went on to write superb tales of his own. So look into your country's myths and legends. Look at the themes emerging from those and write your own fairytales around that. I do wish people wouldn't just dismiss something as "just a fairytale". There's no "just" about a fairytale. There is so much truth in them - and that should be reflected in our own stories too. Honest writing = characters that grip people because they can identify with them.
N = Numpties
I love this Scottish word for idiot. And fairytales do need their idiots (especially if they themselves don't think they're idiots or realise they are). There is great comic potential here for one thing. The Emperor's New Clothes is a great example of a numpty in power! Even the rich and powerful can be taken in by clever conmen. One of the things I love about Puss in Boots is the miller's son knows and accepts the cat is cleverer than he is!
O = Origins
This ties in with M above. Look at the origins of fairytales. Think about the origins of your characters. What made you want to write about them? How do their origins impact on their lives and the stories you are going to write about them?