So. Many. Things.
- Character Development.
If you don’t have this, your characters are lifeless, two dimensional machines. You don’t want that, trust me.
- Grammar/Sentence Structure.
If this isn’t good, you could sound unintelligent and uninteresting. If that’s how the story goes, it won’t be a good read.
- The Dialogue.
Don’t make all your characters have the same speech pattern.
That’s not how it is in real life, it shouldn’t be that way in a story.
DESCRIBE where the characters are. If all you say is “they were in a city”, that’s not very interesting.
Now, if you were to say: “They were in a sprawling metropolis, with modern architecture and busy streets”, that’s interesting.