Exclamation Points

Rule 1. Use an exclamation point to show emotion, emphasis, or surprise.

Examples:
I'm truly shocked by your behavior!
Yay! We won!

Rule 2. An exclamation point replaces a period at the end of a sentence. It also replaces a midsentence comma.

Incorrect: I'm truly shocked by your behavior!.
Correct: I'm truly shocked by your behavior!

Incorrect: "I'm truly shocked by your behavior!," I told her.
Correct: "I'm truly shocked by your behavior!" I told her.

Rule 3. Avoid using an exclamation point in formal business writing.

Rule 4. Overuse of exclamation points is a sign of undisciplined writing. The writer F. Scott Fitzgerald once said, "An exclamation point is like laughing at your own joke." Do not use even one of these marks unless you're convinced it is justified.