Exclamation marks behave in a similar manner to full stops in that they define the end of a sentence. The difference is that they are only used if the sentence expresses excitement or surprise. As with a full stop, when used at the end of a sentence, it is followed by a capital letter.
If you use them too much in a document, It is considered bad writing and that can have a negative effect on your mark. The general principle to follow is that a document should not contain more than one exclamation mark.
Several exclamation marks together is always to be avoided,