Adam Scott Thompson at 2013-11-30 14:26:44:
This is a technique I've employed in my writing and in real life. I observe a person and think, "If they were an animal, what kind would they be?"
Some animals are predatory. Some are highly adaptable. Others only attack when provoked. Others still escape predation by appearing to be a more dangerous creature. Some are social, others solitary. The animal kingdom is vast and so is the spectrum of humanity.
Anyway, I find it helpful to choose an animal for each character that best aligns with their personality and behavior. Animals are basic. Humans under pressure -- the conflict(s) in your story -- become basic. When in doubt ask, "What is this [human] animal's basic reaction?"