Character Clues
Character Analysis
Dialogue
Dialogue is one of the most prominent tools at a playwright's disposal to give an audience information about a character. Now, that doesn't mean that characters just spout off things like, "Well, you know that I am a 32 year-old writer who had a different life than his older brother." At least, in most good plays, dialogue like that doesn't exist.
In dialogue, we often gain insight into character through conflict or through the expression of a specific desire. We get a good sense of Austin and Lee's relationship from almost the top of the show, despite the fact that the two are not talking about their relationship at all:
Austin: You going to be down here very long, Lee?
Lee: Might be. Depends on a few things. […]
Austin: Well, you can stay here as long as I'm here.
Lee: I don't need your permission. (1.1.81-86)
Just from this exchange, we can sense that Austin feels like he is in some way superior to Lee, that Lee recognizes this, and that Lee makes it very clear that he is going to do whatever he wants regardless of what Austin says. It's also possible to delve a little into the subtext to figure out that Austin doesn't really want Lee there. He wants to know how long he's going to have to deal with this situation.
Action
There is an old adage for playwrights that it's always better to "show" than to "tell." Basically, this means that you can learn a lot more about a character from what they do than what they say. So instead of Austin saying something absurd like, "Well, I have turned into something I never thought I would be. I have become some type of animal. I am like my brother now," we see Austin take action, and we know all of this:
(he lunges at Lee whose back is still to him, wraps the cord around LEE'S neck, plants a foot on LEE'S back and pulls back on the cord.) (2.9.246-249)
Description
Theater is, by its nature, a collaborative art form. A playwright creates the story that is being told, but depending on the actors, directors, and designers, that story can vary greatly from production to production. One way the playwright can maintain some control (or at least give control a shot) is to provide detailed description of action, design, and character.
While Shepard doesn't belabor the point when it comes to describing his characters, he does provide hints for actors and directors. Sometimes just a little thing that can give a better understanding of who these people are:
Saul: Well, we ought to get together sometime and have a little game. Austin, do you play?
(SAUL mimes a Johnny Carson swing for AUSTIN) (1.3.54-56)
Just this simple little description of what Saul does provides a clue for the actor who's playing the role. Now, actors can interpret this different ways, but at the very least we know that Saul is a guy who imitates Carson—a big-time performer. We know that there is a little bit of performance in Saul's character, as this is not a natural action in the least, and we might even be able to assume that Saul finds himself amusing. Why else would he do something like this?
Okay, individual actors and directors will make their own interpretations of these people, but Shepard has provided a few things beyond dialogue and pure action that offer clues.