Before the script is written you need to know what will happen by the end of the episode, and break it down further to know what each page has to achieve by the time it ends.

Unlike a novel, a comic strip doesn't have a lot of space to breathe, so you have to try and be informative and entertaining all within 9 panels or so, whilst moving the story forward at the same time!

I'll know from my overall synopsis how much of the story a particular section needs to tell, so I can then do a rough page by page breakdown to make sure each page does its job. There's a balance to achieve here so that the technical aspects of storytelling do not swamp the creative aspects, even though the technique is highly important.