question about the margins for screenwriting can easily be solved
by purchasing a screenwriting program that will automatically
format your script.
1" margins on the top, left, right, and bottom of the page.
lengthy action descriptions or long dialogue (rare in scripts
these days) are not right justified.
the first page, the title is at the top, centered, about half an
inch from the edge of the page. The dialogue is at the
middle and about 2 1/2" from left and right margins.
The character's name in all caps, is centered, at the line above
the dialogue text.
action descriptions are about 1" from left and right margins.
scripts for more information on margins.