A sure fire way to create momentum in your story is by linking scenes together, and to do it often. Specifically, to end a scene with a hook of some sort—say with an action, question, or expectation that is fully, or partially fulfilled in the next.
In Advanced Screenwriting, Linda Seger labels this linking mechanism between scenes as action-reaction. She provides the following examples:
In the film, Traffic, Salazar asks Francisco to provide information about the men who present a threat. The scene ends with Francisco writing down a list of names. The very next scene shows Javier and Manolo getting to the men on the list. The link between those two narrative blocks is airtight and preserves momentum.
In a later scene Javier promises Anna that he’ll find her husband. In the very next scene, he does. And yet later, Francisco is shot, though he doesn’t know who shot him. In the next scene we see an unfamiliar man packing up a rifle. The implication is that he is the one who shot Francisco.
“Action-reaction scenes are airtight. They preserve story pressure.”
Here is an example from the same film where the flow is interrupted because a scene ends on a static note rather than one which links it to the next scene. In this scene Robert’s wife and daughter congratulate him on his being chosen as the new drug czar. His daughter says: “It’s great daddy. It’s just amazing, that’s all.” The scene ends on a statement, rather than a question, intention or demand, which interrupts the momentum.
Transitions can also be a little tricky, especially when an expected ending to an episode is omitted. At one point Gordon says: We have a warrant to search your house, Mrs. Ayala.” The scene ends on the expectation of a search and perhaps the finding of incriminating evidence. Instead, there is a hard break to the story in Mexico. Seger suggests that although the writer need not have necessarily followed up with a scene showing the search of the house, a follow-up scene of some sort that dealt with the warrant more directly ought to have been included. Although the scene in Mexico is a consequence, it feels a little dramatically disconnected—we are left with the sense of a missing reaction scene.
Action-reaction scenes avoid a slackening in momentum, especially in story beats where large changes in narrative time and space occur.