You can slump in your office, a coffee shop, the middle of 394 (depending on how desperate it is) asking questions:
What matters most about this story?
Where do I want my main character’s journey to end?
How do I make the reader care?
You can do this until all your hair turns gray, until you kill the story with your worrying, your prodding.
You can write scenes, possibly out of order. Ones you know won’t end up in the book. Ones that might.
You can put characters together in the grocery store, in class, in their bedrooms, and let them talk.
It’s your choice to trust the process of writing—which promises that eventually (with enough words dropped drown onto the blank page) you will find the answers.