Most of us writers are not trained professionally, so we're learning as we go. Here and there, I learn new things, new little rules that make a difference, rules that mean going back and changing old work, but also better quality for future work.
One rule that meant a change in my old manuscripts was in writing dialogue and the punctuation--when to use a comma and when to use a period. I had been doing it wrong, using a comma whenever I ended a statement and mentioned the person making the statement, such as:
"Let's go," Mark smiled. "I'm hungry."
This is incorrect. There should be a comma if there was a speaking word, such as Mark said, Mark interjected, Mark interrupted, etc. However, like in the case above, he merely smiled. This is not a speaking word, so it needs a punctuation break. The correct form would be:
"Let's go." Mark smiled. "I'm hungry."
Examples of speaking term dialogue:
"I want a lollipop," the child muttered, "but Mom says no."
"Will you come to my house?" the woman asked. "We'd love to have you."
He coughed then said, "Why should I? You know I hate social events."
Examples of non-speaking dialogue separations:
"I want a lollipop." The child's voice was a whine. "But Mom says no."
"Will you come to my house?" The woman's smile was warm and friendly. "We'd love to have you."
He coughed and turned away. "Why should I? You know I hate social events."
In conclusion, if you're using a speaking term, use a
comma separating the dialogue from the person speaking. If it is an
action or another non-speaking term, separate them with a period.