The Mechanics of Dialogue
Commas go inside quotation marks, while colons and semicolons go outside them:
“Go away,” he said.
He said “Go away”: he really wanted me out of there.
Use lower-case letters for your dialogue tag after exclamation and question marks in the dialogue (even though your word-processing program might try to make them upper case).
“I love you!” he exclaimed.
“Who, me?” she wondered.
When your speaker addresses someone by name in dialogue, it should be preceded or followed by a comma.
“Don't get me started, Mom.”
“Katie, you’re driving me crazy!”
Use a new paragraph when a new character (that is, a character other than the one who has just acted or spoken) acts or speaks.
“That’s ridiculous,” I told her. Really, I couldn’t believe she thought I would do that to her.
She gave me a withering look. “Are you sure?”
“I’m totally sure,” I said. But suddenly, I felt uncertain.
Bob came into the room. “IT’S FRIDAY!” he bellowed, totally oblivious to the tension between us.
After a piece of dialogue, use a comma only if what follows is a dialogue tag. This is the biggest mistake students make in writing dialogue, and each time, it yanks me right out of the story.
Wrong: “It’s time to clean up,” he rose from the table.
Right: “It’s time to clean up,” he said, rising from the table.
Right: “It’s time to clean up.” He rose from the table.