Introduction to the story, characters, location and time frame should usually be the start of the screenplay. Setup is an important part as the audiences have knowledge about the movie or the performance. It's better to start with a picture rather than an unknown voice on a blank screen as that will be good to absorb the audience into the story. The image can be of anyone, either that of the actor who plays the central role, or any place like his hometown, whatever conveys the theme? Like in Harry Potter and the Chamber of Secrets, a snake is shown crawling which later gets killed by Potter in order to save himself and the students.
Starting with characters interaction is also a good idea as the audience concentrate on them for a while to decide whether they want to pursue them or not and also keep them wondering about the plot of the story. But it's very important that whatever is portrayed in the first few scenes or the first ten minutes should be directly related to the story. If any irrelevant stuff is being displayed it will simply confuse the audience and can also make them lose interest.
After gaining audience's interest the next ten pages should explain about the unfolding of the story and at the same time holding the suspense of the story. Most of the characters can be introduced, environment can be created, past events can be enacted and the villain can also be introduced but that isn't a must. To build the suspense the villain can be pictured as a good guy but his reality comes to light after a bad incident or when he caught red handed by another character. But this shouldn't take long to test the patience of the viewers.
Next is the catalyst or the inciting incident which creates a twist in the movie. The normal flow of the story should be disrupted. The audience should be kept on their toes so as to retain their interest in the story. Questions like what do the characters want and what is obstructing them should be answered here. After these questions are answered the next question will be very important, that whether the evil-doer will win in his plan. Until this question isn't answered the audience waits for something to happen, they wait for some action or they wait for the climax of the movie. If the antagonist doesn't win the story will have a happy ending and the characters will live happily ever after. But if he does win, then the story will have a tragic end and sometimes will result in the death of the main character. This is known as the first act of the movie.
The catalyst or the inciting incident can be depicted as small scenes which when linked creates a mystery or with the receiving of vital information by some character or as a clash between the good and the bad characters. In the movie "Disturbia" the hero watches reports on the television about missing girls and were later found murdered. In another scene, the hero hears a scream of a girl from his neighbor's house, who is also the antagonist of the movie.
Plot point one is the climax of the movie. It occurs after the first act. They are usually meant to surprise the audience with something unexpected with the occurrence of a pivotal event. The main lead takes a risk and faces his opponent. And if it's a happy ending kind of a movie, the main lead gains victory over the villain by either killing him or making him learn a lesson. And if the story is supposed to have a sad ending, the villain gets away by causing harm to the good character. The last page should give an idea about what the future will be for all the characters and if it's a sequel, it should keep the audience guessing about the future.