Before the camera(s) rolls and audio is recorded, a script is written and a crew is gathered. What that all entails will depend on what the story will be and how big the budget is.
Do you even need a script…? Even a documentary needs a “script” – or at least a list of shots you will need to put together a coherent flow of what is being presented on the screen… Narration should be scripted before hand if you know what you will be filming (taping) when you start your project… Are you just going to stitch together a bunch of images for a narration while music plays in the background…? Or, will you be telling a story…? Either way, you need some sort of a “road map” of what it is you will be filming (taping)…
Examples of script writing software: “Final Draft“, “Arc Studio“, “Fade In” (just some that are available; do a search online for more)
Production software: “StudioBinder“, “DramaQueen“, “Trelby“
