When you're writing the script, do you write a separate backstory or just work elements of one into your script?
Bingo.From my experience, some new writers tend to lose track of their character's backstory in longer pieces--Mom died when s/he was seven but gave him her blessing at his/her wedding. She died early or late, not both. These little mistakes get caught by the audience. So my recommendation is just take a few minutes to write down the character's history beforehand, so you don't get snared down the road. Good luck.
Personally as long as I know why the characters behave the way they do, and have their reasons, I don't need a backstory. Take the villain from Silence of the Lambs for example, nothing more was explained then needed to be. Or you could it like how some writers do, like Tarantino, and just have a lot of backstory, which is unnecessary to the plot, but still their for flavor.
So I'll ask this then.
When you present a script to an actor, do you let them read it first and see what they get out of it? You know, who they think the character is?
Then does the director sit down with the actor and go over the character even more, molding the character into what they both want?