Models follow examples far better than instructions. "Write like this:" with examples

This is a helpful resource your AI can reference, though each model has its own inherent style and preferences: https://tropes.fyi/tropes-md

Instead of having it do the writing, use it as an assistant (research, sample text) and then pick good parts and write it yourself. Examples of your/good writing are indispensable

Depends on who you are writing for too