The process of breaking down the script occurs after the producer reads through the screenplay once. The producer reviews the script, and marks certain elements that need to be taken care of before production, or even before pre-production can begin.
Marking 1/8s 
Each scene, as per slug line, is measured into 1/8s of a page by its number of inches. Most pages of a screenplay are eight inches, so each inch is an 1/8, even if a page exceeds eight inches. The number of 1/8s is then marked in the top left corner of the scene, and circled. If a scene lasts longer than eight 1/8s, it is converted to 1. So, a scene lasting twelve 1/8s is marked 1 4/8.
Marking elements 
To ease future production, an assistant director marks the elements found in each scene. This process repeats for each new scene. By the end, the producer will be able to see which scenes need which elements, and can begin to schedule accordingly. The film industry has a standard for color-coding:
Element color codes 
||Shape or color
||Any speaking actor
||Any stunt that may require a stunt double, or stunt coordinator.
|Extra (Silent bits)
||Any extra needed to perform specifically, but has no lines.
||Any extra or group of extras needed for the background.
||Any special effect required.
||All objects important to the script, or used by an actor.
||Any vehicles, and all animals, especially if it requires an animal trainer.
||Sounds or music requiring specific use on set. Not sounds added in during post.
||Specific costumes needed for production, and also for continuity if a costume gets ripped up, or dirtied throughout the movie.
||Any make-up or hair attention needed. Common for scars and blood.
||If a scene requires the use of more uncommon equipment, (e.g. crane, underwater camera, etc.).
||For all other questions about how a scene will go, or confusion about how something happens.