I'll be brief.
Correct:
"This is good," said Dumbledore. "Ten points for Gryffindor!"
Incorrect:
"This is good." said Dumbledore. "Ten points for Gryffindor!"
"This is good." He said. "Ten points for Gryffindor!"
"This is good," Said Dumbledore. "Ten points for Gryffindor!"
OR if periods/full stops turn you on so much you can't write anything without them, use action tags instead.
Correct:
"This is good." Dumbledore smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
Incorrect:
"This is good," he smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
"This is good," He smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
Said tags (said, shouted, whispered, thought, and others) should go with a comma. Unless your sentence ends with "!" or "?" of course.
Action tags (laughed, punched, he bought time as he gathered his mana) should go with a period/full stop.
There's no explanation for it, this is just how it is (or there is! I don't know. Someone teach me, please).
Correct:
"This is good," said Dumbledore. "Ten points for Gryffindor!"
Incorrect:
"This is good." said Dumbledore. "Ten points for Gryffindor!"
"This is good." He said. "Ten points for Gryffindor!"
"This is good," Said Dumbledore. "Ten points for Gryffindor!"
OR if periods/full stops turn you on so much you can't write anything without them, use action tags instead.
Correct:
"This is good." Dumbledore smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
Incorrect:
"This is good," he smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
"This is good," He smiled/danced/picked his nose/twerked. "Ten points for Gryffindor!"
Said tags (said, shouted, whispered, thought, and others) should go with a comma. Unless your sentence ends with "!" or "?" of course.
Action tags (laughed, punched, he bought time as he gathered his mana) should go with a period/full stop.
There's no explanation for it, this is just how it is (or there is! I don't know. Someone teach me, please).