There is no formula for having a great idea – but to begin your writing, you do need, at least, some kind of idea. Then you need to find ways to turn your idea into something a reader would enjoy reading. This is the creative part, taking something ordinary and turning it into something extraordinary.
For example, think about writing a description of a coastline. You might start to think straight away about a crowded beach - children playing, deck chairs, sun shining, happy sounds; but, if you stop for a moment, you’ll recall that that's been done before. It's okay, but it's hardly original.
What about turning that idea on its head - not a crowded beach, but a deserted beach? Not summer, but winter? Not lovely and inviting, but covered in oil and polluted? It's not a pretty picture, but it's original - and that gives impact.
When you tell a friend a story of something real that happened in life, you’ll build it up around a climax of action, but tell it in a way that keeps your friend interested and listening. Maybe you saw a footballer break his leg during a Saturday match and you then tell it at school on Monday.
A written story isn’t face-to-face and you don’t know the reader and this means you’ll need more elaboration, explanation and detail – but you can still write it in a very similar way to how you might tell it. Even everyday incidents can make very effective stories if you elaborate and dramatise, add detail and explanation, always keeping a sense of tension till the end. Your reader, like your listening friend, enjoys wondering 'where it all is leading' and 'what will happen next'.