Begin a new paragraph with every change of speaker.

Incorrect:
“Hello, Mary,” Jeffrey stammered. “Hi, Jeffrey, how are you?” “Uh, fine. What have you been doing lately?”

Correct:
“Hello, Mary,” Jeffrey stammered.

“Hi, Jeffrey, how are you?”

“Uh, fine. What have you been doing lately?”

For quotations longer than a single paragraph, put quotation marks at the beginning of each paragraph but only at the end of the final quoted word.

This is the only case in which an opening quotation mark may not have a matching closing quotation mark.

Example:
Carton continued: “I see that child who lay upon her bosom and who bore my name, a man winning his way up in that path of life which once was mine. I see him winning it so well, that my name is made illustrious there by the bright light of his. I see the blots I threw upon it faded away. I see him, foremost of thee just judges and honored men, bringing a boy of my name, with a forehead that I know and golden hair, to this place–then fair to look upon, with not a trace of this day’s disfigurement–and I hear him tell the child my story, with a tender and faltering voice.
“It is a far, far better thing that I do, than I have ever done; it is a far, far better rest that I go to than I have ever known.”

(Because the quotation is longer than a paragraph, note that the first paragraph has no closing quotation marks. Quotation marks do open the next paragraph to show that the quotation continues.)