"Notice the negative space as shapes in their own right."
~Dr. Fehr
Utilize the Visual Art concept of Negative Space to refocus your play and strengthen your edges.
During a rewrite, to combat writer's block, or to resurrect an unsuccessful script from the grave.
This functions as a perspective switcher for me, so if you're needing a set of fresh eyes, this might help.
"Negative space, in art, is the space around and between the subject(s) of an image. Negative space may be most evident when the space around a subject, and not the subject itself... Negative space can be used to depict a subject in a chosen medium by showing everything around the subject but not the subject itself. ...give equal attention to the positive and negative shapes [and] the result is often a much more accurate [depiction]."
If you are in the early stages of writing a script it is entirely possible that you haven't fully explored the potential of the characters, situations, actions, and/or other elements of your script that you relegated (literally) to the background in order to obtain that cherished first draft. Perhaps you were overly focused on the story line, or the plot twist, or the background story, or the main character, or the theme, or the sound effect of the wind that whistled outside the creaky window. Thinking in terms of negative space can reveal the currently under-formed (unfocused/blurry) parts of the world you've created. Most of the time a script contains many references (explicit or not) to realities outside the bounds of the conversations or actions happening on the page: a girlfriend away at work, a deceased father-in-law, a potted plant. Perhaps your focus was on the story itself instead of the characters. Perhaps your focus was on poetic language at the expense of clear meaning. Perhaps your focus was on a somber mood instead of on rhythm. Put simply, negative space means the parts you weren't intentionally trying to write (but were partially formed anyway).
At this point you've completed the exercise and you should have perceived a change in the script. Hopefully you've taken a non-dominant element in your first draft and explored it fully. Perhaps this added something unique to your perceptions about your play and perhaps it didn't. Either way you should have a clearer focus not only of the lines drew in your first draft but also of the lines you hope to draw. Happy writing.