Screen the movie again before you write, even if you've seen it fairly recently. This time, take notes as you watch. You'll be amazed at the details that you had forgotten since the last time you watched the film. Note the story details, information about the characters, the things they say, how they speak as well as how they interact with others.
Review your notes soon after the screening so you can begin writing while the story is still fresh in your mind. Explain the time period in which the story takes place. Tell the reader whether it's a drama, a comedy or a tragedy, and discuss which sub-group of those categories it occupies.
The film may be a romantic comedy, a farce, slapstick or a dark comedy. If it's a drama, it might be a crime story, a courtroom saga, an action adventure, a story of political intrigue or science fiction. A tragedy usually results in the death of the film's hero or heroine, or another crucial protagonist in the final scenes.
Write about the film's art direction, its sound, musical soundtrack, lighting and any special effects. Explain whether or not these technical elements help to create a believable experience for the viewer. Explain how all of these elements fit together to help tell the movie's story. If appropriate, talk about makeup, hair design and theatrical scenery used in the production.
Discuss in your essay the actors who play major roles in the film. Explain whether or not these actors were well cast for their roles. If they were particularly adept of playing their characters, briefly recount some memorable scenes in which they most effectively inhabited the characters they portrayed.
Evaluate the director's work. Tell the reader what parts of the film were well staged and offer examples of scenes that helped make the story come alive. Explain how the director's craft was crucial to this particular screenplay. If appropriate, you can speculate on how other directors might have handled the same project, either successfully or unsuccessfully.