DON'T SERVE UP BIG CHUNKS OF NARRATIVE
If your paragraphs are over three sentences, consider breaking them up into smaller, more digestible chunks. White spaces do not only keep the pages looking clean, they just make the whole thing easier on the eyes.
Huge slabs of words look unappetizing and ultimately turn us off. You want to establish a free and loose rhythm with short paragraphs so the reader's eyes will move quickly down the page, devouring words. There's a psychology at work here. Screenplays are works of action; they must move nimbly.
If your script resembles a 19th century Russian novel, then the reader will feel like he has to slog his way through it, no matter what the content. Making your script appealing to read is not merely cosmetic, it is crucial.
IF THE CAMERA CAN'T SHOW IT, THEN WE CAN'T SEE IT
EXT - BUSY CITY STREET - DAY
JADE, a conservative, no-nonsense gal who graduated Yale third in her class, stands on the street corner and hails a cab.
Did we witness her being conservative and no-nonsense in any way? Did anyone mention where she went to school and how well she did? If not, then how can we possibly know this?
These attributes can easily be revealed by some illuminating actions or dialogue. But unless we can actually see it on screen, we can't know it. Remember the limitations of the camera lens.
KEEP THE CAMERA INVISIBLE
There is nothing more distracting and frustrating than trying to become absorbed in the flow of narration and having it constantly interrupted by speed bumps like CLOSE ON, PULL BACK, DOLLY UP, PAN DOWN and a truckload of other needless directions. Reading camera shot after camera shot in the narration is not just supremely annoying, it wrecks the rhythm.
Remember, your script is a reading script, not a shooting script. It should flow like a story with dialogue and narration. Never mind the technical angles and calling every single shot, as those will be determined by the director anyway. Just captivate us with a good story and let us visualize it in our heads.