its usually plot first
from there divide it to scenes
then make the script
IIRC thats what is told to me in a convention i was in a few years ago
they also mention something about a registering your work to the writer's guild i cant remember the full details but i think it got something to do with copyrights of your work(or is it the other convention i was in not really sure just check it out for yourself)
anyways
send me your script would like to try making the artwork for you
chibi's and monsters are my specialty
richard_ulysis_devilla(at)yahoo(dot)com