In a bad movie, things seem to happen for no apparent reason, just for the convenience of the plot. In a good movie, things make sense, but you may need to explain more than necessary to get there.
Look for any James Cameron script on the Internet and you’ll see scenes that over explain everything, but which were cut out of the final movie. After reading the script, you can see why they were cut since they were largely redundant and unnecessary. However, from a screenwriter’s point of view, they’re necessary because they explain what happens.
In the actual film, these scenes prove unnecessary but by knowing what really happens, James Cameron could direct and edit his films to get that idea across without slowing the film down.
In “Aliens,” James Cameron wrote a short scene where a family is living on the planet where Ripley first found the original Alien. The boy and girl talk about how they play in the ventilation ducts. Later when the aliens have wiped out most of the colony, Ripley discovers the little girl has survived by hiding in the ventilation ducts.
By cutting out this explanation, we don’t know how the little girl learned about the ventilation ducts, but it’s not a crucial part of the story that we accept it as valid when we see how the ventilation ducts help the girl survive. It’s a simple scene that helped James Cameron write, but proved unnecessary in the actual film.
In “Terminator 2,” the liquid metal Terminator has just murdered John Connor’s foster dad. Later as the evil Terminator looks around the house for a clue to where John Connor might go next, he walks past the bathroom where we see John Connor’s foster mother dead in the shower.
Then we see the evil Terminator reading letters from Sarah Connor to John and he sees the address. That’s how he knows where Sarah is located.
However, this scene probably got cut because earlier, Arnold (the good Terminator) tells John not to rescue his mom because the liquid metal Terminator will assume that’s the most likely place to find John again. That brief mention is enough to make it believable that the liquid metal Terminator would try to reach Sarah Connor so we don’t need the complete scene of the evil Terminator finding Sarah Connor’s letters in John’s room.
These two examples show that a scene should serve multiple purposes, not just to convey a single bit of information. If a scene does nothing but convey information, that information can likely be introduced somewhere else in a much shorter span of time.
Read other scripts on the Internet and you can see how they might differ from the original. In a draft of “Star Wars,” Luke actually meets his father who is in charge of the attack on the Death Star. Also in this early “Star Wars” draft, Hans had a third companion, a clunky robot that’s always breaking down.
Hans and a Wookie are enough, so tossing in a third character simply clutters the movie, so George Lucas wisely cut it out. The idea of a script is to use as few words, scenes, and dialogue to say as much as possible. The less you present while still telling your story, the more effective your story will be.
When writing your own screenplay, don’t be afraid to overwrite, but look for ways to condense or eliminate scenes. You want your story to flow rapidly and keep the audience enthralled. Too much explanation can ultimately slow down your story’s momentum and stop it altogether, and that’s definitely not what you want.