Here’s how you can tell if a scene is working. Does your scene tell a mini-story with characters striving for a goal and then achieving it (or not)? If so, then your scene works. If not, then your scene needs to be dumped or reworked.
Look at the beginning of a scene and the end. The beginning should state a problem or goal of some kind and the end should resolve that goal in some way. Basically, the beginning and ending of every scene must show some kind of change.
Think of the scene in “Star Wars” where Luke has just freed Princess Leia from her prison cell. Suddenly, storm troopers cut them off from escape so Princess Leia opens a grating and everyone dives through to escape the storm troopers. End of scene.
Notice the change? One moment they’re trapped and by the end of the scene, they’ve escaped.
Of course, every scene directly leads to a new problem so the next scene in “Star Wars” occurs when they realize they’re trapped in a garbage compactor with no way out. To make matters worse, the walls start crushing the garbage. By the end of this scene, Luke has managed to get R2D2 to stop the walls from moving. End of scene, problem solved.
Every scene constantly creates a problem, the problem gets worse, and then by the end of the scene, the problem gets resolved in some way. Typically the solution to the problem creates a new problem later for the next scene.
In “Babe” there’s a scene where the farmer thinks Babe, a pig, has killed some sheep. So the farmer takes Babe into a shed and cocks a shotgun to kill Babe. Just as he aims the gun to shoot Babe, the farmer’s wife comes running to let the farmer know that the police caught some dogs that were killing sheep. That’s when the farmer lowers the gun and realizes Babe didn’t kill the sheep after all.
The problem was that the farmer thinks Babe killed his sheep. The end of the scene shows the farmer learning Babe is innocent.
Every scene must show some kind of change by initiating a problem and resolving it by the end of the scene. If a scene doesn’t initiate a problem, the scene action will seem pointless. If a scene doesn’t resolve a problem it initiated, then the scene will feel inconclusive and unsatisfying because it doesn’t lead anywhere.
It’s easy to write scenes that begin with a problem that is never resolved in anyway. That leads to disappointment because audiences want some type of resolution and the screenwriter fails to deliver. When you order food at a restaurant, you expect to get it. If you don’t get your food (or get the wrong food), you’re disappointed. That’s the same feeling audiences feel when a scene creates a problem but fails to resolve it in some way.
So examine every scene in your screenplay and decide whether it initiates a problem and resolves it (while making the problem worse in between). If not, then your scene probably needs work.