“Cut out all those exclamation marks. An exclamation mark is like laughing at your own jokes.”
— F. Scott Fitzgerald —

EXCLAMATION POINT

The sign used in writing after an exclamation or interjections, expressing strong emotion or astonishment, or to indicate a command.
AVOID OVERUSE!

An exclamation point is used to express strong emotion.
“No!” he yelled. “Do it now!”

An exclamation point may be used to close questions that are meant to convey extreme emotion.
What on earth are you doing! Stop!

An exclamation point can be inserted within parentheses to emphasize a word within a sentence.
We have some really(!) cool tattoos on sale this week.
Note that there is no space between the last letter of the word so emphasized and the parentheses. This device should be used rarely, if ever, in formal text.

An exclamation point will often accompany mimetically produced sounds.
“All night long, the dogs woof! in my neighbor’s yard.”
“The bear went Grr!, and I went left.”

If an exclamation point is part of an italicized or underlined title, make sure that the exclamation point is also italicized or underlined:
My favorite book is, Oh the Places You’ll Go!

(Do not add a period after such a sentence that ends with the title’s exclamation mark. The exclamation point will also suffice to end the sentence.) If the exclamation point is not part of a sentence-ending title, don’t italicize the exclamation point.
I’ve asked you not to sing la Marseillaise!

— Capital Community College Foundation
Guide to Grammar and Writing —