by Michael Chasin  Screenwriting Mentor, IAFT/Miami

Clint Eastwood famously said, “50% of a great movie is having a great script—and 90% of the other 50%—is in the casting.”

It is difficult to find fault with Mr. Eastwood, given his legendary career as a director.

If we were to write a film for Mr. Eastwood to act in, his character description in the screenplay might read, he’s a thin, six-foot four-inch eighty year-old with a gravelly voice.

Should Mr. Eastwood choose not to act in our film, well then, where would we find a thin, six-foot four-inch eighty year-old with a gravelly voice?

The answer is—we wouldn’t need to.

For Silver Linings Playbook, director David O. Russell had no intention of casting then 21-year-old Jennifer Lawrence, believing she was too young to play a widow against 37-year-old Bradley Cooper.

Her audition changed his mind.

“There’s expressiveness in her eyes and in her face, that many stars have to work for, that’s ageless,” he said.

The result of that casting—an Academy Award for Ms. Lawrence—and of course, an excellent film.

With that in mind, we might, on second draft, change our Eastwood character description to, he carries the many decades of his hard life on his face, and in his voice.

The talent to express that weariness can be found in all shapes and sizes.

So great casting—that 90% of the remaining 50%—is in identifying the emotion of the character to be cast—and then finding the talent to express that emotion.