Grammar: The Exclamation Mark [ ! ]
The exclamation mark is exclusively a feature of quoted speech and informal English. It has no place in academic writing.
Its uses are two. The first is with imperatives, but only if they are truly commands –
Do as you’re told!
Keep off the grass!
Stop picking your nose!
This includes imperatives expressed as wishes –
I wish you’d stop doing that!
but not imperatives expressed as questions –
Why don’t you leave me alone?
Exclamation marks are not used with imperatives that are contextually requests, invitations or statements of advice –
Give me your number again.
Have another beer.
Don’t mention it.
Vote for Jones.
The second use of the exclamation mark is with interjections (words or expressions of emotion) –
Informally, of course, the exclamation mark may be used more freely to illustrate surprise or to draw attention to something important –
I didn’t find out myself till last week!
The meeting has been brought forward from the 19th to the 12th!
But like question marks, one is quite sufficient.