Screenwriting Structure

The three-act structure of a film is essential to any screenwriter who needs to learn about plotting a screenplay. Strategically placed climaxes and lulls contribute to the overall pacing of the screenplay and serve to thrill audiences.
Screenwriting Guide on Plot Structure and the Alternative
There are two schools of thought on whether the three-act structure to a screenplay is always necessary. Some believe it is essential to every story. Others believe it takes an autocratic viewpoint and is discarded altogether. It has been done successfully, as can be seen in such films as Eraserhead and Apocalypse Now. However, it is a useful tool to have within the screenwriter’s kit and can be utilised in making the most of the story and in compelling the  script reader to keep turning the pages. Perhaps it is better to know about it, than to continue in ignorance.
What is the Three Act Structure of a Screenplay? 

Some sort of structure is necessary to hold the story together. Without it, the screenplay might appear to be a random set of scenes without a sense of culmination. Indeed, audiences are confronted with the three part structure when reading books and watching films. It serves to entice, thrill and provide breathers between climaxes. Briefly, the model screenplay is thought to consist of three parts:

Act 1: The Set-up. This forms the opening of the screenplay, and includes the hook, the inciting moment, and the onset of the main conflict.

Act 2: The Conflict. This consists of the main body of the screenplay, and includes a series of culminating climaxes and lulls, leading up to the point of no return.

Act 3: The Climax. The final third of the screenplay includes the final climax, and the rug-pulling moment, where it is all or nothing. Loose ends are also tied up at the end.

To simplify matters, consider the story of The Wizard of Oz based on L Frank Baum’s book, set out on an average length screenplay of 100 pages. Note that one page of a screenplay equals one minute of screen-time.
Act One of the Movie: The Set-up, the Hook and the Inciting Moment

In Act one, we are introduced to Dorothy and her ordinary life on a Kansas farm, which provides some form of reference from which a fantastic story develops. The hook is provided at the very beginning when she meets a dubious character passing through town. The inciting moment is provided by the incident when Toto, Dorothy's dog, is confiscated by Mrs Gulch for biting her. The beginning of act two explodes onto the screen in the form of a tornado that transports Dorothy to the Land of Oz where her goal to get back home is now clear.

Ideally, act one will be around 25 pages long. The hook will be introduced before page 10 and the inciting moment will occur before the end of act 1.

Act Two: The Main Conflict and the Point of No Return
The main conflict will occur within Act 2. Each climax will be higher than the last, and lulls strategically placed to provide the audience with a breather. Dorothy meets her foe, the wicked witch, whose menace contrasts effectively with Dorothy's three friends. The point of no return occurs when Dorothy faces the Wizard and is trapped into promising him the witch’s broomstick if he would agree to get her home.

Act 2 will usually occur between pages 25 and 75. The point of no return will occur at around page 45 to 50.

Act Three, the Climax, the Ultimate Plot Twist and the Resolution

The ultimate climax of act 3 sees Dorothy facing doom in the witch’s tower and her friends trying to rescue her. Just when Dorothy and her friends are ready to meet their end, Dorothy manages to overcome the witch in an unusual turn. She returns to Oz with the witch’s broom. The ultimate plot twist occurs when Dorothy discovers that the Wizard is but an ordinary man, and he does not have the power to send her home. Suddenly, her quest seems impossible. Of course, she realises at the end that she had the power to get herself home all along.

How to Write Play Scripts with a Compelling Plot

Familiarising oneself with the three-part structure of writing the screenplay means that the screenwriter might wish to experiment with this formula or use it to solve problems with the script in regards to the placement of climaxes and lulls.
Copyright Rachel Shirley 2009