What does every book on writing say?

"Show, don't tell."

You hear this advice a lot and will continue to hear it over and over and over until one day you are writing something and you stop, think and rewrite it to show and not tell the audience the piece of information you want them to know. 

In the current screenplay I'm working on, I wrote a nice little monologue for one my characters explaining to another character why another character is getting on his last nerve. I read it, then went back to the beginning of the scene and added more scenes showing how that character is getting on the character's nerves. 

The monologue revealed how I was explaining to the audience information that needed to be shown to them, so they could see it for themselves before he tries to explain it to another character. In this way the audience knows something the other characters do not until the character's feelings are said out loud to another character and all the cards are laid out on the table.