Developed by Lee Strasberg who first taught at the Actors Studio in New York then founded the Lee Strasberg Theatre and Film Institute, the Method style of acting is focused on having an actor create real thoughts, emotions and memories of the characters he's playing so that the character feels as real as the actor playing the role. Method acting is designed to inhabit a character so thoroughly that the actor "lives" the character even when he isn't in front of the camera. The main tool for Method acting is the use of sense memory which requires an actor to use his senses to remember objects and experiences that he can later summon during scenes that express sorrow, anger and sadness. Famous practitioners of the Method acting style include Marlon Brando, James Dean, Paul Newman and Meryl Streep.
Stanford Meisner was a student of Lee Strasberg who later rejected the notion of sense memory in favor of his own style that emphasized specific behavior arising from an actor's response to his surroundings and to other people. The primary training for the Meisner acting style is a repetition exercise in which two actors face each other and repeat a phrase over and over until the words take on new meanings with new tones, inflections and intentions. The goal of the exercise is to free the actors from thinking and to allow them to just respond to the other person in a real way and to stay in the moment of that situation. Meisner's style of acting is meant to produce emotional and honest performances that lack artifice and feel lived-in and real because Meisner-style actors are trained to stay in the moment. Famous adherents of this style are Robert Duvall, Grace Kelly, Gregory Peck and Diane Keaton.
Stella Adler was an actress and acting teacher who developed the Adler style of acting which emphasized that an actor must always do something in a scene. Adler believed actors should break down their scripts into verbs beginning with the word "To," so for example if a scene describes an actor trying to convince someone to do something, the action would be "To seduce." This allows actors to know exactly why they're performing a scene. The Adler style involves extensive research and the use of the body as a physical instrument. The actor's voice must be clear and expressive. Actors that practice this style of acting include Robert DeNiro, Harvey Keitel, Benicio Del Toro, Naomi Watts, Ed Norton and Salma Hayek.
The classical style of acting --- sometimes referred to as the Shakespearean style --- originates from British theater productions performed on the stage. Classical acting is a more refined, controlled style that emphasizes precision of dialogue delivery. Classical actors often commit the entire script or stage play to memory. In contrast to the Method style which incorporates improvisation, classical style acting is technical and exact and rarely veers from the written page. Because it has its roots in 18th and 19th century stage plays often performed in outdoor theaters, classical acting can sometimes seem theatrical, especially in film adaptations of famous plays. Sir Laurence Olivier, Sir John Gielgud, Sir Anthony Hopkins, Dame Glenda Jackson, Dame Judy Dench and Dame Helen Mirren are all students of the classical acting style.