Zero. Or maybe one. But zero is usually enough.
I hunted for exclamation marks in To Kill a Mockingbird, voted “America’s best-loved novel” in PBS’s Great American Read and winner of the Pulitzer Prize. I reached page 15 before I found one, the only one in the first chapter. “My stars, Dill!” said Jem.
In the first chapter of For Whom the Bell Tolls by Ernest Hemingway, I could not find a single exclamation mark. In the first 20 pages of a book nominated unanimously for the Pulitzer Prize (though denied because the head of the Pulitzer board found the book offensive) and written by an author who eventually won the Nobel Prize for literature, not a single exclamation mark.
Let’s try one more, a biography this time, David McCullough’s John Adams, another winner of the Pulitzer Prize. The text begins on page 17 of my edition, and the first exclamation mark I found is on page 28. “Oh, that I was a soldier!” Adams wrote to his wife.
When might you use exclamation marks? They are used to show strong reactions or commands. But use them sparingly. They show the subtlety of a sledge hammer. And exclamation marks can make writing seem juvenile.
Don’t use exclamation marks adjacent to other sentence punctuation. ?! is wrong. .! is wrong. ,! is wrong. So is !!!!! One exclamation is sufficient, or more likely, superfluous.
If you tend to write using exclamation marks, go back and delete half of them. Then go back and delete half again. For the remaining exclamation marks, justify using each one. Try using stronger verbs rather than depending on exclamation marks for emphasis.