If I allow a secondary character to become too involved with influencing the plot, I run the risk of diluting the story s focus and making a muddy mess of things. This is a very common problem with new writers. Veteran writers know better. Or, we at least know what our options would be. The key to understanding how a character will do a thing is to look at the character s traits.
All characters have strengths and weaknesses, likes and dislikes.
These traits will influence how he or she does what is done. The actor wants to know why he s been asked to brush his teeth before sleeping. It may sound absurd, but the actor might be justified in asking the question. Suppose this character has just broken out of a foul prison in Libya. The outer goal and the inner need are two very different things.