The most important thing a director does during the making of a moving image is to maintain the main theme of the work during the three stages of pre-production, production and post-production. After studying the script, the director breaks it down into small pieces called sequences, scenes and plans, and prepares a text called decoupage. This text is a recipe for all the factors that make up the film, in which all the details of the plan are written, such as the angle of the camera, the scale, the movement and speech of the actor, the light, the time, the place, and so on. The director must be proficient in the principles and rules of all stages of production in order to be able to lead the group well and achieve the desired result.

The principles of framing, rhythm, continuity of movement, sound and image are some of the rules that the director uses for decoupage. Contrary to the principles of natural sciences, these artistic rules are not very fixed and unchangeable, but are the result of the experiences and preferences of previous directors and vary according to the type of attitude and artistic style of the filmmaker.

The person accompanying the director on this journey is the assistant director, who assists the director in his work and performs some of his tasks, including filming, arranging transportation, coordinating with various groups, and inviting individuals. Needed for the location of the filming, maintaining order and tranquility on the set, controlling the budget and doing whatever the director entrusts to him. Sometimes a movie requires more than one assistant, and the presence of a second or third assistant is required, especially in large projects.