The film industry uses several abbreviations as shortcuts in scripts. It's up to you whether you use these abbreviations or not. Some readers find them distracting, while others prefer the shorthand. We've already discussed several -- O.S., O.C., V.O. -- which are specific to scripts. Here are some others.
b.g. = background
b.g. is used in an action paragraph.
Frankie sits on the bed tying his shoes. In the b.g., Julie takes money out of his wallet. She also pockets his car keys.
CGI = computer generated image
CGI denotes action that cannot be filmed normally and will require the use of computers to generate the full imagery, as used in films like The Matrix.
CGI: His mouth begins to melt, then disappears entirely.
f.g. = foreground
f.g. is used in action the same as b.g., except the action takes place in the foreground.
SFX = sound effects
SFX tells the sound people an effect is needed.
SFX: The BLAST of a train whistle
SPFX = special effects
SPFX announces that a special effect is necessary (one that might not require the use of CGI).
SPFX: A beam of light illuminates Frankie's face. His features slowly melt like a wax figure.
M.O.S. = without sound
The story goes that a German-born director (perhaps Josef von Sternberg, who discovered Marlene Dietrich) wanted to shoot a scene without sound and told the crew to shoot "mit out sound," a phrase which the crew found humorous and thus proliferated it. It is most commonly used to show impending impact of some kind.
M.O.S. Horses stampeding down Main Street.
POV = point of view
The camera 'sees' the action from a specific character's position
JULIE'S POV - Frankie sits on the bed tying his shoes.
A MONTAGE is a cinematic device used to show a series of scenes, all related and building to some conclusion. Although a French word, it was created by Russian director Sergei Eisenstein as a "montage of attractions" to elicit emotions on several levels. Most often it is used as a passage of time device. Think of a baby being born, then rolling over, then taking its first steps, and finally running through the sprinklers. For example:
MONTAGE 1) Josh is born. The doctors clean him and hand him over to his smiling mother. 2) Josh rolls over in his playpen. His mother applauds. 3) Holding on to the coffee table, Josh takes his first steps. His mother joyously hugs him. 4) Clad in droopy diapers, Josh runs gleefully through the sprinklers. His mother sighs, and reaches for the diaper bag.
You can also number the scenes A), B), C) if you prefer. Either numbering format is correct. (Note that the mother's emotions change through the montage from joy to weariness, once Josh is completely ambulant there should be some element of the story that a montage will illustrate.)
The MONTAGE is formatted as a single shot, with the subsequent scenes action elements of the complete sequence. It isn't necessary, but some writers write END OF MONTAGE when the montage is completed.