You need to know the conventions (or tropes) to write genre stories — what elements readers expect to find and what plot structure you should use. To learn these things you have to spend a lot of time reading novels and watching films — or you could read this in-depth series where the work has been done for you.
Books in the series:
Other titles for writers:
- Plot Basics: Plot Your Novel or Screenplay in Eight Sequences
- Character Creation: A Guide to Archetypes, Motivation & Emotion for Writers & Actors