An exclamation mark is generally used at the end of a sentence to give a sense of excitement or surprise, for example: ‘I can’t believe he beat me!’
Using an exclamation mark is pretty straightforward, just be wary of the tone that it gives to your writing. Note the difference:
- I can’t believe he beat me.
- I can’t believe he beat me!
The first might be said with slumped shoulders and a pout while the second might be said with disbelief and anger or surprise.
An exclamation mark is only ever used ONCE at the end of a sentence, regardless of how excited or surprised one may be. ‘!!!’ means the same as ‘!’ therefore it is unnecessary to use more than one exclamation mark.