Each scene should move the story forward in terms of both plot and
character. The scene you are now writing should be motivated by a
previous scene, and should motivate the next. One creates anticipation
for another in cause and effect. If the central character gets involved
your scene is probably moving the story forward. All scenes should
direct us to the Showdown at the end, which is the biggest scene, or
sequence of scenes, in the movie. What is the payoff for this scene?
Who do I need this scene? What is my purpose for this scene? Does the
scene reveal something new about a character and/or story? At the end,
does the audience want to know what happens next?
Never tell what you can show. Be as visual as possible. Rather than
someone talking about someone doing something, show us that person
showing us that thing.
Avoid talking heads. Add events behind just two people talking.
Every dramatic unit has a beginning, middle, and end.