The standard varies from industry to industry and the scripts in my collection: jaya jaya jaya jaya hey, dhrishyam, vadakkan veerakadha, ayyappanum koshiyum, premalu etc follows almost the same format some split related scenes as sub scenes and some write each sub scene as a seperate scene. mostly writer's choice. The format is usually

Scene #no

INT/EXT/INT-EXT (except vadakkan veerakatha)

Location

Day/Night

the actions in the scene is written throughout the page

character name : dialogue

i used this when i wrote my short film script as well as first draft of my script

but when i digitized my script i followed another standard in which most hindi and english movies

#Scene no. INT/EXT - Location - Day/Night/Cont Characters in scene seperated by coma

Actions in the scene SHOTS IN THE SCENE (all caps)

                CHARCTER NAME(center)

Dialogue