“This is your daily, friendly reminder to use commas instead of periods during the dialogue of your story,” she said with a smile.
“Unless you are following the dialogue with an action and not a dialogue tag.” He took a deep breath and sat back down after making the clarifying statement.
“However,” she added, shifting in her seat, “it’s appropriate to use a comma if there’s action in the middle of a sentence.”
(Source: theclonewriter, via cthulhu-with-a-fez)