The most flagrant way a writer demonstrates contempt for his readers is by ignoring punctuation altogether. A close second is the abundant use of the exclamation point. Some writers even use three or more exclamation points, lest the reader not fully grasp the significance of what is being said.
To be effective, the exclamation point should be used in moderation.
At the end of a sentence
The exclamation point is a mark of terminal punctuation. As such, it should not be followed by a period or question mark. Some writers will use both a question mark and exclamation point for an exclamatory question, but only the exclamation point is truly necessary.
What in the world are you doing up there!
What in the world are you doing up there?!
There is a punctuation mark that combines the question mark and exclamation point. It is called the interrobang, and it looks like this: ‽ Yet, for reasons already explained, it is hardly needed.
The greatest confusion arises when exclamation points and other punctuation marks appear at the end of a sentence. For examples of most such pairings, see the terminal punctuation chart.
In the middle of a sentence
When a quotation ends with an exclamation point, a comma that would ordinarily be placed inside the closing quotation mark is omitted.
“Get out,” Marcus said.
“Get out!” Marcus yelled.
“Get out!,” Marcus yelled.
As part of a title of work
If the exclamation point is part of a title of work or a proper noun, the comma should be retained.
His latest short story, “Don’t Make a Sound!,” is his most suspenseful yet.
Her first novel, Excite!, was a critical hit.
After five years in the sales department at Yahoo!, he took a marketing job at Google.
As editorial comment
Writers sometimes place an exclamation point in brackets to indicate their surprise or amusement at something being quoted. Avoid this in formal writing.