Tag! Your Character is it.
What's a tag? It's the description of the character the first time he appears in a screenplay. It's the one time in screenwriting that the writer is permitted to write details that will only be read by the actors and director. Though if you've crafted your story correctly, the viewing audience will pick up on the characteristics that you outline in your tag.
What makes a good tag? It's the spot-on definition of character traits. Spoiled. Arrogant. Pissed at the world. Always in a hurry. Too good for mankind. Everyone's friend. Mild-mannered. A doormat.
And what of looks? Only tell us physical details if they are pertinent to what makes the character who she is. For example, you might write: BRENDA DILLON (13), the tallest girl in the school and painfully aware of that fact. She's also the best Center in the state of Nebraska, but that's hardly just compensation for the pain of always being the wallflower at junior high dances.
You wouldn't want to describe Brenda as six foot tall. Why not? What if the best actor for the part was five foot seven? You don't want to force your casting director to choose a runner-up simply because the actor fits the height requirement. This way you allow your casting director and production team to work together to make sure the supporting actors are shorter. Remember: filmmaking is a collaborative process.
The best way to get a good feel for how to write tags is to read them in screenplays. If they gave an award for best tag ever written, I'd argue loudly that it be granted to Mark Andrus, screenwriter of AS GOOD AS IT GETS, for his description of Melvin Udell (played by Jack Nicholson). Melvin is described as:
"...well past 50, unliked, unloved, and unsettling. A huge pain in the ass to everyone's he's ever met."
Now that's a tag an actor can sink his teeth into. See the movie if you haven't already; you'll witness how the screenwriter, director, and actor brought Melvin to life exactly as the character was tagged.
An optional exercise today: use the photos to describe what kind of character is behind them. I'll post my own ideas in a day or two.