There is a lot of stuff written about how to define your character. It's all about background, motivation, personal goals. That's all good. But one of the fundamental questions that people often forget is "How will they react in a given situation?"
People react in different ways. Different situations might bring out different reactions. There are innummerable shades in the reaction spectrum. Some reactions are subtle, some are more pronounced, and others are downright scary.
In action movies, where adrenalin fuels every decision, there are two primal reactions: Fight or Flight. These reactions are common throughout the entire animal kingdom so you can use it for any character - human, animal or alien.
Basically, when you are faced with a situation, you have two choices - Run for your life, or fight for your life. If you know how your character will usually behave you can easily plot their course through the whole film (especially the ups and downs of Act 2).
Here are some traits of flight/flight characters that might help you think through the possibilities:
Flight
- Careful. Looks before they leap
- Avoids the main conflict
- Plans for eventual success, not short term gain
- Good fit for a spy, sniper, or stalker
- Intelligent. Won't do anything until it's been throught through
- Might let a friend get captured rather than risk blowing a good plan
- Likely to trap the enemy or force them to make a mistake
- Could manipulate people to do the dirty work for them
- When they fail they just create a new plan
Fight
- Brash. Gets in the face of the enemy
- Seeks out conflict. Runs toward the biggest noise
- Jumps in without all the information
- Often the walking wounded
- Wins through sheer force
- Fights through a million henchmen to get to the big boss
- Will put themselves in harms way to protect the innocent
- When they fail it's the end of the world
So, try to put your characters in one of those categories and then make sure all of their behaviour is consistant with it. You can ramp up the tension and the jeopardy, but the core or the character shouldn’t change.
