Many scripts have a simple structure comprised of three acts. The first act lays out the locations along with the characters and their motivations, and in many cases, sets the tone for the movie or play. The hero is typically established in the first act. The second act involves expanding the plot. The hero is usually presented with obstacles he must overcome or given a task to accomplish. The third act is the conclusion; the various strands of the story are tied together and resolved. Typically, the middle act is the longest.
Scripts must be formatted in a specific way. Adherence to these technical conventions is very important as it helps others visualize your work. The font used is typically Courier New and the font size should be 12. This may seem a small point, but it's very important. One page of script written in this style translates to roughly one minute of screen time, so agents can approximate the length of a film by the weight of the script.
Each scene must have a heading, known as a slugline, noting where the scene takes place. A typical slugline (always capitalized) might read "EXT. LAS VEGAS STRIP - SUNSET." In this example, EXT stands for exterior.
Each dialog line must start with the character's name. Consider the opening lines of Hamlet:
BERNARDO: Who's there?
FRANCISCO: Nay, answer me: stand, and unfold yourself.
BERNARDO: Long live the king!
Another convention is to ensure that all unscripted sections, such as scene descriptions and directions for actors, are written in the present tense, e.g., "a door opens," rather than "a door is opened." This makes it easier for the reader to imagine the action unfolding. To facilitate this, ensure you use active voice during these segments.
Film scripts must also describe the shots are used in each scene. There are a wide variety of camera angles, so while writing your script you must carefully consider which one would be best suited to shoot the scene and mention it underneath the slugline in all capital letters. The most common camera angles are overhead shot, or bird's eye view; long shot, medium shot, closeup, and extreme closeup; panning shot, where the camera moves horizontally while the cameraman stands still; Point of View (POV) shot, where the audience sees the action through the eyes of a specific character; and low angle shot, where the camera is looking up at a character or object.