One of the most common script issues I see is that screenwriters often seem to forget that the people who will be portraying their characters are called "actors" and not "talkers." So many scenes appear to exist solely for the purpose of getting a few characters together so that they can expose information to each other and then move on to a restaurant or someone's house so they can all sit down and talk some more. The characters in these scenes don't do anything other than move around from one part of the room to another and then react to to what other characters are sighing, often by sighing, glaring, or smiling broadly.
(Note: If there's any sighing glaring or smiling broadly in your screenplay, there's an excellent chance that you should remove it. This would probably be a good place to put a smiley face or something so that I don't look like such a curmudgeon, which I totally am. Smiley face.)
Imagine watching a scene like this in a movie:
INT. KITCHEN - DAY
Mary enters and leans against the refrigerator. John is standing by a window, staring out into the vast suburban sprawl of their middle-class neighborhood.
I can't live like this any more. You've become so
distant, John. So angry.
Why can't you see how tormented I've become
ever since the death of my father? Don't you know
that we had unresolved issues? Unresolved issues!!
I don't care about your unresolved issues, John.
I care about the future of my unborn child.
That's right, John. I'm pregnant and it's not your
baby. I'm leaving you, John, and I would prefer
it if you didn't come after me.
Mary turns and walks to the door. She pauses for just a moment, but then boldly strides through the door into her new future.
Obviously, that scene is set in a boring location and is full of unnecessary dialogue and inconsequential actions. Here's an alternative to that scene that might be more effective:
INT. INVESTMENT BANKING OFFICE - DAY
Elaborate Christmas decorations festoon the office for a holiday party. John gives a toast to dozens of employees.
Those hippies can protest all they want, but we
just had the best fourth quarter in the history of--
Mary strides into the office. She drops a pregnancy test stick into John's drink. It's positive.
It's not yours. Get your shit out of my house
As she exits, Mary throws her wedding ring at John's assistant, Gwen.
That setting allows Mary to publicly humiliate John and also changes the mood dramatically from the beginning to the end of the scene. Mary does almost all of this without dialogue, only telling John and the audience the things we wouldn't be able to infer from her actions.
The important takeaways from this scene are:
1) If one of your characters tells another character a piece of information, see if you can show that information visually instead.
2) Look at the location of each of your scenes and make sure that it helps to get across the message of that scene or to underscore the action. If you have a scene that's set in a living room or a restaurant, chances are that the location is not contributing anything to your scene.