To write a movie screenplay in four months, a writer can outline, remember the importance of the hero's journey, and always keep the intended audience in mind. Outlining is critical for avoiding writer's block, as it allows writers to front-load big story decisions. Once the outline is complete, the writer may have decisions left to make, but the basic structure of the film is set in stone.
The hero's journey is a process that is central to making any movie engrossing. To speed up the writing process, writers can focus on scenes that explicitly move the protagonist forward toward personal change. Keeping the audience in mind is often a very motivational practice. With the agenda of surprising and mystifying the audience firmly internalized, writers can experience rejuvenated creativity.
Another way to speed up this process is to write with a specific star in mind. Having a face and a voice for the main character helps the writer maintain dynamism and enthusiasm. Reading scripts out loud can reveal dialogue problems efficiently, which can in turn lead to faster screenplay completion. It is also wise to keep the classic, three-stage story structure in mind. Each film that follows this structure has a discrete beginning, middle and conclusion.