One last quote from Anthony Minghella's interview with Shooting People, this time on writing characters (and I think this applies to novels, scripts, everything):
“Nobody thinks I am a minor character in my life and so I have always wanted to write as if you could walk off with anybody who came into the film... And I often write more story than I can tell for them… And I have also tried not to pass judgment on people because I feel like again nobody wakes up in the morning and says 'Oh I’m the bad guy in my story' or 'I am the good guy in my story.' We are all of us trying to make sense of how we are and sometimes we behave well and sometimes we behave badly. And if our stories are otherwise then they don't reflect the truth of what it is like to be in the world.”