This would be heavily informed by the genre of the film you are writing about. I would recommend reading some other descriptive essays within the genre/time period/film movement to see how other writers made their words come alive. I think the task requires a little creativity! You might also want to focus on structure quite intensely. A word I always managed to throw into my film essays: visceral. Always fits for some reason!

Unless your assignment actually says you should follow a specific pattern or template, don't worry too much "what things you should cover." Don't try to say everything that can be said about the movie. Try to think of a small number of points to make. Try to make them original and interesting. Think of three things about this film that are important to know about this film. They would not be the same for every film. If you are not a cinema expert, the things that are important to you are different from the things that are important to an expert. Be yourself; don't try to sound like an expert if you aren't one. Try to mention specific facts about the film, things that are true of this film and not others. If you state an opinion, follow it with a fact that supports the opinion. For example, "This is a very long film; the running time is 2 hours, 51 minutes." The "cinematography" is the camera work. It includes things like whether the film used close-ups or far shots, whether the colors were bright or subdued, whether everything in the scene always in focus or whether the actors were sharp and the background behind them blurred. But if you did not notice the cinematography, you would not mention it. For example, "Jacque Tati's 'Playtime' is shot in color, but according to [source] Tati tried to give it a black-and-white 'look," using greyish sets and costumes, The "score" is all of the musical background in the film. Again, you would not mention it if it did not seem important. "John William's score in 'Star Wars' is very important in setting moods and convey the epic sweep of the movie. Williams' score is in the style of classical music." The "editing" or "cutting" means the sequence and pattern of the shots or cuts in the film. One movie might use "long takes," another movie might use "quick cuts." "Alfred Hitchcock's movie, 'Rope,' looks as if it were filmed in one single 'take' 80 minutes long, with no cuts at all."

Go to imdb.com and pick your favorite movie then use the plot synopsis as your guide

Guau, Jerome, how collaborative and supportive you are. I think you could have saved your comment. I´m asking collaborative people for providing me with adjectives opninions or advice to write it. Prejudices like yours are not benefitial to communities where people learn from each others despite the fact that they may pay for proffesional lessons as I do. Obviously, I won´t pay for your services.

So you would like someone to write the essay for you? :)