Whoever is writing a script whether it be you or even any film or tv scriptwriters, they always have to make sure that the size of their font is 12 and that the style of the text is set to courier. So the font will be 12-point courier font.
Here is a video demonstrating how you should format and structure your script with the dialogue, actions, expressions and movements of the characters. The script in this video is being done using a screenplay programme called celts.
Here is an example from The Bourne Supremacy:
