Read the script a few times. Try to understand its genre, story and truth. Focus on what is actually there, instead of trying to find any possible hidden meanings. Appreciate the plot as it is and let it reveal its message to you without interfering.
Get to know all the characters. Start getting more involved in the plot and experience the story's characters and the world in which they exist. Do not just focus on your character, rather try to keep your character a part of the group of people that make the world of the screenplay. Study what they do and at the same time, look for thoughts or beliefs behind their words and actions. Examine their relationships and the reasons they were put in the story in the first place. Determine every character's purpose in moving the plot forward.
Break down the different scenes. Ask yourself what is happening in every scene of the screenplay. Establish the time and place where each event occurs. Sometimes this information is unclear, so it is up to you to look for hints that will tell you where or when a scene takes place. Define the purpose of each scene in the film and determine how it helps in moving the story forward.
Focus on your character. Define your character's main characteristics, assets and flaws. Determine his goals and list his actions when trying to achieve these goals. Establish your character's conflict and his relationships with the other characters of the screenplay. Determine what makes this character different than others in the story. Look for subtext in his words and actions, give him depth and a solid background.