You'll need characters and genre, and perhaps an overall goal. After that it's all about scenarios.
The general guideline for any story is that they follow this pattern:
Intro - Goal - Conflict - Resolution.
Intro to introduce (duh, goal to establish the point of the story/scenario, conflict being some sort of obstacle that needs to be overcome and resolution being the ending.
Books can be very helpful but I reckon the important training comes from experiance.