Yesterday, Littlestar and I went to see True West at the San Jose Stage Company. It was nice to see a play in such a small venue.
As we'd gone with a mass of animation/illustration students, there was a Q&A with the actors afterward. This showing of True West featured:
Joanne Engelhardt
Rod Gnapp
Randall King
Gary S. Martinez
Though I didn't take extensive notes, Gary noted (and everyone agreed) that you primarily look to the text to understand your character -- both in your character's lines and in what else is said about that character. Joanne Engelhardt, for example, only appears late in the play, but the first five lines of the play describe her character, such that you have an image of her in your head the whole time.
Given this emphasis on the text, and the fact that they were working from the material of a solid playwright (Sam Shepard), I ended up asking, "What do you do when the text is bad?"
Rod gave me an answer that I found helpful for character motivation in general: "Pick an objective and an action." He also described it as, "A desire and a verb."
So, basic character = Objective + Action or Desire + Verb
Good way to look at it.