In a sense what I'm looking for are the underlying rules of the show, the things you'd want to know if you were going to write on it. (I'll even sometimes write a document, "Five Things You Need to Know if You're Going to Write on ER (or whatever)".
One way of getting to those rules is via the process of watching a whole bunch of episodes themselves, which I highly recommend. When you go into a series ready to learn what it's doing, the patterns can really pop out.
But there's another way of doing some of this, too, a way that can be really helpful when you're first hired on a show. It's two simple steps:
First, Come up with a logline. If you had created this series, what would your one line elevator pitch be?
Don't settle for just one logline. Come up with a bunch, as a way of getting at different angles on the show.
So for instance:
FRINGE is the story of a mad scientist who saved his son and destroyed a universe.
FRINGE is the story of a son forced to take care of the father who ruined his life.
FRINGE is the story of an FBI agent drawn into a world of insane science experiments that begin to bring back memories of things done to her as a child.
Second, make lists. Loglines are like the airport workers walking the tarmac with light up rods to direct the planes: they give us directions to go with episode pitches.
If you're going to be on FRINGE, what kind of episodes should you be offering? The loglines make it clear: ones about crazy science ideas and scientists, fathers and sons and vulnerable children. So knowing that, you can brainstorm lists of ideas on each topic.
Read through a list of FRINGE episodes, and what do you find? A never ending set of insane science-based ideas like jumping into dreams, ideas absorbed via osmosis, a gas that makes your skin self-seal, a drug that turns you into a human porcupine, an anti-grav medicine. Many also involve a father who is trying to save a son (usually at the cost of the lives of others). And some involve adults preying upon children.
You find a logline, you find a path.
