Writing dialogue for a story can be a real challenge. The problem arises from the simple fact that dialogue in your written masterpiece is not accurate reflection of the dialogue that actually takes place between people in the real world.
Communication between us human beings is a funny thing. Although we think of it as an expression of vocal sound waves, it is not. Our ability to communicate is based on everything from the body language we use, facial expressions we make, the pitch of our voice and, yes, the words we use. Dialogue in a book contains only one of these elements.
Do a test to full grasp the difference between written and spoke dialogue. Picture a scene between two people. Now write down a subject to be discussed between those two. Break out something to record a conversation and then have at it. Present both sides of the argument until you come to a conclusion. Take a break for 10 minutes and then come back and write out the conversation. Transcribe what you recorded and compare then two.
The first thing you will note is the grammar of voice communication is entirely different than that of the written conversation. We speak horribly! There are plenty of incomplete thoughts. This arises from the fact we unconsciously complete the rest of the thought with body language or pitch of voice.
The second thing you will note is the dull nature of the voiced dialogue. A