See how the pros do it before you dive ahead. Go to Rottentomatoes and see how the top critics write film reviews. Or you can go to the individual websites of various newspapers around the word and search for the name of the movie you're interested in seeing or reviewing in their search boxes, if they have any.
Summarize the plot without giving away any major twists or specific scene descriptions. These are called "spoilers". If you include spoilers in your review, you may ruin the movie-watching experience for your readers. Be as ambiguous as possible. If you do choose to include spoilers in your review, do your readers the courtesy of warning them in the first few sentences of your article that you will be giving away plot details.
Be critical without being offensive. You do not have to use bad language or be overly sarcastic to show your distain for a particular scene, actor or the entire movie in general. It is up to the reader to decide whether they should go see the movie. Therefore, if there is something you don't like, describe its weakness and why you think it didn't work.
Pinpoint specific strengths about the film, such as particularly moving scenes, the use of good scenery and sound effects, constumes and make-up and the performance of one or more actors or actresses.
Make references to other films, performances of actors, classic or contemporary literature or other aspects of pop culture, if possible. Filmmakers often borrow certain elements or even bits of dialogue from others, and not only from other movies.
Make note of the directing style, camera angles and other visual aspects of the film. This is optional but is very likely to appeal more to the hardcore movie buffs and film students, who are among your readers.
Finally, note the technical details of the film you are reviewing, such as the main actors, director, executive producer, studios or production companies, running time and audience rating.