An exclamation mark (!) is used to indicate a sudden order, intensity of emotion
(such as surprise) or volume. It is used after an exclamation.
Examples:
Get off! I was on
time! It's a
pike!
Avoid using exclamation mark in formal writing - they are considered somewhat
crass. In official correspondence, your power of expression needs to be strong
enough the negate the need for exclamation marks. Also, using two or more
exclamation marks consecutively is considered rude or juvenile.