What do Actors do, think etc.

Actors are tools of the directors in the production process. They show the themes and ideas behind a film. They try and connect with the audience on an emotional level as well as embody the character as described by the writer. There are many acting methods and the actor needs to find one that will work in the situation.
Sometimes the actor will have some creative control and discuss things with the designers and other team members about costume, look, motive etc. Acting usually involves waiting around, obeying the director and being fresh and ready at a moments notice.