Rule of Thumb: In a properly formatted script, if there are more than five lines of dialogue under a character name, it’s starting to become a speech. Too many speeches and your script is too “talky.”
Strike every “well,” “now,” “listen,” “oh,” etc. that you find in your dialogue. Actors put those in where it’s natural to do so and they only make a script harder to read.
Delete the “pleasantries” and “chit-chat” from scenes. You’re just wasting time, boring the reader and keeping them from YOUR story.
Try this: See just how terse you can make the dialogue. Terseness helps to create impact and makes characters seem more forceful and decisive in a drama and funnier in a comedy. When it gets to the point where you’re feeling a little uncomfortable with the directness, it’s probably about right.
Say the lines out loud as you write them. It’s amazing how much this helps.
TIP: Try and name your characters with names that start with different letters of the alphabet. so that when you type the first letter of a character’s name, you don’t have to sift through a list of them to get to the one you need.