One common novice screenwriting mistake is to dump exposition in the dialogue of characters so they wind up telling each other everything that they already know. This flaw can even be seen in “Vertigo,” Alfred Hitchcock’s film where the hero asks a woman, “Weren’t we engaged once?”
Instead of dumping exposition clumsily in dialogue where it serves no purpose other than to sound fake, a far better technique is to use something called “attack with exposition.” This means use exposition as a weapon against a character.
Rather than have one character tell another one, “Remember, you’re an alcoholic.” Have the two characters argue and get progressively angrier and angrier. Then one character could shout out, “I should know never to trust an alcoholic.”
Notice this gets the same information across (someone’s an alcoholic) without sounding fake. Because the exposition is used to attack another character, it’s not only more memorable, it’s also more natural and realistic.
Exposition is inevitable, but you don’t have to make it a dry exercise of stilted dialogue. Instead, make your dialogue sting with verbal attacks that inadvertently reveal something about each character’s past that’s important. The more you use exposition as a tool to attack others, the better the audience will remember the exposition at all. Highly charged emotions simply make exposition memorable.
Remember that phrase, “attack with exposition.” When you do that, chances are good your exposition will feel far more natural and interesting as well.