Second Commandment

#2: "Thou shalt not let the reader get lost"
Whatascript: 
The answer may be obvious, but why is this second commandment important?

Formatman: 
When you hear the reader say these lines from the TV series Chuck about your screenplay: 
- Where am I? Is this a bathroom? 
- No! This is hell! 
Then you know the reader got lost and you blew it. Your movie script just got closer to get tossed to the pile of "Pass".

Whatascript: 
How do you avoid this dreadful perspective?

Formatman: 
By using 2 elements of screenplay format, master and secondary scene headings (also called sluglines).

Screenplay format first element: master headings
Whatascript: 
Formatman, let's first talk about master scene heading. What is it? 

Formatman: 
In screenplay format, a master scene heading, also called primary slug line, is a one line of text in a screenplay that comes before the description of a scene. 
It gives a framework for the whole scene. 
It is as if everything that happens in the whole scene - what is seen, what is heard and where it all happens - is filmed in a single continuous shot, a master shot. Therefore the name of master scene heading. 

Whatascript: 
How does this screenplay format element look like? 

Formatman: 
    EXT. DOWNTOWN LOS ANGELES - DAY
 
    INT. PARIS AIRPORT - NIGHT
 
Whatascript: 
It seems they are 3 parts... 

FormatMan: 
Correct. In screenplay format, a master heading is made of:
the camera location,
the scene location and
the time
1. Camera location
Whatascript: 
Let's talk about the first part, camera location. 

Formatman: 
Well, you have basically 2 choices:

INT. (for Interior) - the scene takes place inside a building
or 
EXT. (for Exterior) - the scene takes place outside a building
It is usually clear where you are and therefore which one you need to use. 

Whatascript: 
Why is that important? 

Formatman: 
It tells the production crew if they will be shooting on stage or on location. That impacts the budget. 

Whatascript: 
Can you give us some examples? 

Formatman: 
From Dead Poets Society, written by Tom Schulman: 
1. On stage shooting:
    INT. WELTON ACADEMY HALLWAY - DAY   
    INT. CHURCH ENTRANCE - DAY
    INT. DORMATORY - DAY
2. On location shooting:
    EXT. SCHOOL GROUNDS - DAY   
    EXT. ROAD - NIGHT
    EXT. RIVER - DAY
Whatascript: 
Is it possible to combine INT. and EXT.? 

Formatman 
Yes. In some cases, screenwriters use INT./EXT. or EXT./INT. when a scene takes place both inside and outside. The first term used indicates where the scene starts. 3 examples: 

1) From "The Cider House Rules", written by John Irving: 
    INT./EXT. ORPHANAGE - DAY

    Faces in the windows; the orphans watch Hazel walking across 
    the snowy lawn with her new parents.
   
2) From "American History X", written by David McKenna: 
    INT./EXT. BEDROOM - DEREK'S POV
    
    He looks through the blinds and stares at the UNMARKED
    CAR. Danny throws his backpack on the bed and exits.
    
3) From "Ali", written by Stephen J. Rivele & Christopher Wilkinson and Eric Roth & Michael Mann - with this time an EXT./INT. camera location: 
    EXT./INT. THE UNITED STATES ARMED FORCES STATION, HOUSTON -
    LOBBY - CHAUNCEY ESKRIDGE - DAY
    
    waits at the curb as Ali and Herbert pull up and get out of
    a car...move through the crowd...reporters shouting
    questions at him we don't hear, go up the steps, into the
    lobby, joining other recruits and M.P.'s.