Basically my preparation is always my personal experience. Plus the impression of the people around me and the director's guidance. And I have a lot of sensitivity to my co-actors and that helps me a lot. What is your emotional state on a set. I like all of the three but theatre is the one that truly excites me.
Theatre is the only ground for an actor to prepare.
The process of rehearsal is the most important for theatre. It goes on for 30 days. And after that hard work the audience response plays on the character. For exposure to a different medium and to a different audience. Every activity has a different type of audience and you want to relate to all kinds of audience.