I'm big on preplanning. I start with ideas, not stories. So even if I have an idea I decide what the themes and philosophy of the idea is instead of structuring a story first.

Basic idea:

So i want to write a story on the horror of consciousness. So i wanna explore how fragile and fragmented consciousness really is, especially when placed in an alien context. That the mind is intricately tied to the body, and breaking that connection results in existential madness.

Story that could explore this:

In a scientific experiment, the consciousness of a predator and a prey animal are swapped to study how their behaviors and survival instincts change. What begins as a seemingly straightforward study spirals into a nightmarish descent into madness as each consciousness struggles to adapt to a body designed for the opposite role in the food chain.

This swap allows me to write about existential horror, where both creatures grapple with primal fear and alien 'sensory overload'. They can't even grasp the lir emotions.

(I'm actually not sure if I wanna go down this route for the story but its an option).

Stylistic choices:

For a story like this I know i can use some typical writing tools, like split povs, stream of consciousness writing and elements of body horror and eldritch madness as the aesthetic guides to dictate feeling and genre. (Although I'm not happy with the story and will probably go down some other route for the very same idea since I do wanna explore that).

Now i know a lot about the story from a simple exercise of knowing what I wanted in the first place. When you know the purpose your story serves your narrative can be more cohesive.

Similarly you can create a one paragraph summary of your story. Then write a one page descriptive summary. Then break that page into chapters or thirds. As you break it down and add details you create something very clear and concise. This is a more formulaic technique I've sometimes used for novella length writing. I find it fun.