You can also start a new paragraph when one character is delivering a long piece of dialogue, but changes subject. For example: "Here is my first paragraph. I am really looking forward to BioShock Infinite, as I've been posting all over the Flood for the last few days. I pre-ordered from shopto.net, but it didn't arrive early. "This is my new paragraph about the slightly different subject of shopto delivering pretty much everything else a day early, at one point delivering DmC on the Friday before the Tuesday on which it launched." Same speaker, different topics, new paragraph. Also, in such a circumstance, omit a speech mark from the end of the first paragraph, letting the reader know it is the same speaker.