The most important thing to remember when you set out to write a screenplay is that you are writing for a visual medium. You must therefore write only what the cameraman can film and the soundman can record.
From the very first moment you should be thinking in terms of what can be seen. A character suffering from some deep angst must show his troubles through his actions or words, though good actors might be able to display this with a look, but you don’t know who’s going to be cast in your piece.
A screenplay is not a work of literature, but the plan from which other creative people will work and add their skills and creativity. Your screenplay will go through the hands of actors, a director, a producer, a cinematographer, a sound man, a set designer, a costume mistress, a props master and many more, and each will have something to say about what your film should be. Whatever ego you’ve built up in writing the screenplay may soon be dissolved, it’s not going to be your baby anymore. And finally, when the movie’s edited and ready, the marketing people get hold of it and sell your romantic comedy as a horror picture!
The mechanics of putting the screenplay on paper are easy enough to learn. They should consist of the following :-