Script Breakdown
A script breakdown is the process of figuring out everything you need to film every scene within the script. For example: cast, costumes, animations, props, setting, sound effects, and so on. This is done to make sure you have everything in order before you actually start shooting, because things go much faster for everyone involved. It’s all about being about to shoot efficiently, not about following any rules here. Since every script it different, just make your decisions based on what will affect your production schedule. I’ve just laid out some ideas on how to get started.
Once you have the script breakdown, you are then able to budget and schedule more precisely. The better you budget and schedule, the less money you’ll have to cough up if you go over, especially on a contracted shoot.
The first task is to breakdown the script into each separate scene. There is no reason to shoot the script in sequence. The best choice is to always shoot by location. It just makes more sense and saves time and money if you shoot all the scenes in 1 location and then move onto the next.
Go through the script again and mark everything that affects the scene: cast, extras, costumes, setting, animation, effects, atmosphere, special effects, props, sound effect/music, and hair.
If it couldn’t get any more work for you, the script itself doesn’t tell you everything you need to know. You need to sit down with the director and fill in the blanks with what his/her vision for each scene is. The slug says day, but what exact time of day? Many times a script will have basic descriptions of clothes, setting, props, ect and you need to know how everything will look before you get started.
Here is a breakdown sheet I made in word that is an edited version for the standard breakdown for SL Machinima. If you are using Celtx, I believe that there is a feature in it for this. Scroll down to see an explanation of each box.

Cast: List the major cast members in the scene. You need to schedule the production around everyone’s schedule and knowing exactly which scenes they are in makes this much easier.
Extras: Nothing adds depth to a scene better then extras. These are typically non-speaking parts.
Atmosphere: Is it raining? Snowing? Overcast?
Costumes: This is not the place for detailed explanations of what everything looks like. Just put the general wardrobe in this box. While we do carry all the clothes on every avatar, it’s helpful to list them all out so when you are looking for/commissioning custom work you can easily make a list of everything needed.
Animations: Since we can upload any type of animation, you will need to gather every single movement each character and extra makes before shooting. Listing them here will help with looking for and commissioning these.
Props: List all the props you need to have for the scene here. This includes items the actors are holding/interacting with and items they are not.
Hair/Skin: Have something specific needed for hair/skin/tattoos/ect? List it here.
Music/Sound: If anything in the scene calls for a specific piece of sound, list it here.
Scripts: Need LSL scripts made for objects to move, interact or anything else? List here.
Special Effects: Need something blown up? How about some sort of particle effect? Seems a bit redundant to have both scripts and special effects since you typically need a script for a special effect, but many times you need a script when it’s not exactly a special effect.
Production Notes: If you have anything left over that doesn’t fit in the other boxes, this is a good place to put it.