We teach acting classes in NYC, with an emphasis on television and film acting. Many of our students are skilled stage actors, who are in many ways relearning the craft of acting for the purpose of doing film and television.
One of the things that presents a challenge for actors in film is that films are often shot out of sequence. Your may spend your first day shooting the last scene in a film, and vice versa. This can be discombobulating for actors new to film. As an actor, you are immersed in your character's motivations and emotions, which (hopefully) evolve during the course of the story. Sometimes your character may begin as one person, and end up as a very different kind of person because of how the events of the story change them. Herein is the challenge.
It is very important that you are attentive to the points in the story where these changes occur. You may want to make notes in your script about who your character is at that particular point in time, so you can navigate shooting out of sequence with ease.
Be prepared to time-travel through your character's life with the awesome technology of film. :)