Each scene is broken into several categories that will help you later in Pre-Production. These categories are:

INT/EXT - The location of the shot: Interrior or Exterior
LOCATION - Where it is exactly: a room, a beach, the White House, etc...
DAY/NIGHT - When this time scene takes place

Example:
INT. BASEMENT - NIGHT

This line is followed by a description of what is going on and who is in the scene.

Example:
JOE stumbles over a box in the dark. A small 40 Watt bulb is the only light.

(NB: When a character is first introduced, their name is in all caps. After this first time, the name reverts to normal capitalization.)

This action is typically followed by speech, whether narration or from the person on screen.

Example:
JOE
Curses!

Speech is either followed by more speech, or by concluding action.

Example:
Joe sets the box upright again, and shuffles toward the lightswitch.

(NB. If the speech is from the same character the line is written:

JOE (CONT'D)
That really hurt.

But if the line is from a narrator, the line is written:

NARRATOR (VO)
Joe is just your average guy. A bumbling man, hoping for more from life.

("VO" stands for Voice Over.)

If the scene ends here, two empty lines follow before the next scene begins.

Example:
Joe sets the box upright again, and shuffles toward the lightswitch.


EXT. JOE'S HOUSE - NIGHT