Every time you switch speakers, start a new paragraph.

You may need paragraphs within a single speaker’s speech. If this happens, only the final paragraph gets final quotation marks.

example:

"Can’t you come up with an interesting example, this time?" asked George.

"Sure", said Martha. "I can wax poetic about that guy at the coffee shop. That one who was sculpting the dragon. HE had talent. And gorgeous hair and eyes. Not to mention, when I talked to him, he could discourse on anything. Brilliant, talented, and gorgeous.

"Or would you prefer I spoke of you? Of your warted nose and a chin that stops before it begins. Of hair so coarse and wiry that it hurts to run a hand over it. Teeth so…"

"Stop Stop! I liked the boring examples better."