I would say that one of the most dominant styles of acting in the film is the use of the Stanislavsky approach by the actors. There is an emphasis on realism in the film. The characters engage in song and dance almost suddenly, outside of reality. However, there is a realism beneath the acting of the players and one that underscores their performance. The viewer believes Bernardo's skepticism, Maria's zeal, as well as Tony's unwavering commitment to "something." The acting style is one that seeks to bring these characters alive through reality. Emotions are absorbed in a realistic manner. When Maria finds out that Bernardo is dead and Tony is the murderer, she rushes to her bed and looks up to God, in a prayer that is realistic with her character. Chino broods in a realistic manner, up to the end when his bullet is both his emotional redemption and the cause of further pain. In describing the Stanislavsky style of acting and how it is carried out by actors, one sees how this is relevant to West Side Story:
...that the actor must experience real emotion, that he must identify with the character he is portraying, that he may use his own past emotional experiences, and above all, that he must learn to speak and behave naturally, as a human being in life.
This style is evident in the film and something that is embodied by the actors in it.