Sometimes those roles with fewer lines can be more difficult to prepare because we have less information about the character. Your job is to fill in the blanks. In order to find the strongest choice, figure out what the whole story is about and how your character fits into it. If it’s a one or two line co-star, chances are your purpose is to reveal more about one of the main characters or to help move the story forward. You might just be exposition, so resist the temptation to make the scene about your character. If you cut your character out of the script, what is missing? That’s a good place to start when you are trying to figure out the reason for your character in the story.
Within context of the story, start to make choices about the surrounding circumstances and your character’s relationship with the other character(s) and their point of view of what is happening. Then, rather than focusing on how to say the line(s), understand what their behavior is and go from there.
Remember, acting is behaving. And behavior is a manifestation of our inner emotional life. Your character, even with one to three lines, is a full human being with inner life to explore.
Find sides for a character with just a few lines and practice understanding where they fit into the story. Make some choices about their point of view, relationships and surrounding circumstances just to see how many different things you can do with the scene. Remember that you don’t want to take away from the whole story. Storytelling is a collaboration, and your co-star role is one piece of a much bigger puzzle. Your job is not to show off your talent. Your job is to serve the story. Have fun and break legs!