5. Be Critical Of Your Exposition
Exposition is a narrative technique which serves to provide backstory to the audience: every movie has tons of the stuff, though it's your job as the writer to make sure that nobody really notices when you're using it. It's not always that easy to hide, though, and there are good writers out there (Christopher Nolan, for example) who aren't particularly good with exposition. When going over your script, though, I can't recommend enough that you try your best to find
better ways to employ exposition. The worse case of exposition overload comes in the form of an "information dump," which is one character tells another character something they already know because the screenwriter needs to tell the audience about it. In reality, moments like this rarely occur. Why would somebody say something that they knew somebody else already knew? That's to say, read your script and genuinely be honest with yourself. Would a character really say, to a co-worker who had experienced the same situation, the following line?
"Remember last year when the lab exploded? Fifty people died... we couldn't get back into the building for weeks. The boss went nuts and starting firing people all over the place. It was crazy."
I doubt it, because all he would have really needed to have said is "Remember last year?" and the other character would have known what was being discussed. The rest of the information is just for our benefit. But it's possible to give across the same information without making it obvious:
"Well, we don't want a repeat of last year. I can't go to that many funerals in the space of a week again. And nobody around here is gonna put up with the boss if he starts firing people."
The phrasing is slightly different, but this time somebody could get those points across and it make sense. It's not a great line of dialogue, of course (an out of context example, at best) but you get the idea. Tweaking this kind of thing in your own script is of huge importance: there's nothing that will take you out of a movie faster than a clunky line of exposition. It instantly reminds you that somebody sat down, wrote the line and - worst of all - tried to sneak it past you. It's a certified mood killer, for sure.