Serenity RPG - Basics of Playing
You’ll find lots of examples, modifying circumstances, and optional rules starting on page 139 of the PDF. Important thing to remember is the basic mechanic of the game:
Attribute + Skill = Result
When someone tries to do something, he rolls the appropriate dice and generates a total. High numbers generally mean success, low numbers indicate failure. The game situation and the number rolled give the Game Master a starting point to describe how a given action plays out—the more imaginative and descriptive the better.
Sometimes you just don’t have the know-how needed for a situation. A ship’s mechanic may have to pick up a gun to defend herself. A doctor may have to take the helm of a shuttle and attempt an emergency landing. A mercenary thug might be asked to give a speech in the town square. When this happens, you gotta roll anyway. When you have an Attribute but no Skill, you roll the Attribute alone.
Here are some detailed analysis of the Serenity RPG system: