Chuck Jones' 'rules'.

When creating the character and scenarios for the RoadRunner cartoon segment in Looneytoons. Creator Chuck Jones created a set of rules that they must obide by when creating the cartoon. For example, one of the rules was that the coyote may never harm the road runner and the road runner may not harm it, but only mock it by saying "meep meep". This is an example of rules in a production.

The road runner never actually touches the Coyote.

Films tend to have rules aswell depending on the genre and also just filming in general. An example of this is the 180 degree rule, this means that the camera must never flip over to the other side of a conversation during a scene, this is because if done otherwise the audience can gbecome confused with whats going on, on screen.