What is the main difference between a shot vs. a set up?
The main difference between a shot and a set up is the sequence in which they are ordered. Shots are a series of clips that make up a scene, and a set up is grouping similar shots together to shoot them at the same time, saving the crew the of time from having to reconfigure the camera, lighting and other aspects of the set from shot to shot.
What is the most important thing to keep in mind with set ups?
The most important thing to keep in mind regarding shots and set ups when going to shoot a scene is minimizing the number of unnecessary turnarounds by grouping similar shots together into set ups. Turnarounds are the instances where lighting, the set and camera direction are reconfigured for a different shot. More often than not, that means the scene will be filmed out of order.
One quick way to use setups efficiently is to organize similar shots/shots of characters in the initial shot list. Preparing this ahead of time will allow the crew to get started right away, and producers will love your preparation and organization.