Place an exclamation mark at the end of a sentence if you are trying to express shock or surprise. For instance, if you are dictating a letter to a friend, you can form a sentence such as "I'm getting married!" or "I've got a new job!". The exclamation mark in both such cases indicates joy and surprise.
Write an exclamation mark to indicate force and threat. This is the case, for instance, if a teenager puts a "Keep Out!" sign on his bedroom door or if you get a letter from an estranged, angry partner, such as "Stay away from me and the kids!".
Pay attention to where in a sentence you place an exclamation mark. Exclamation marks should be placed at the end of a sentence rather than directly after an expression of surprise. For instance, "Brilliant news!, I've won a million dollars" is an incorrect usage, whereas "Brilliant news, I've won a million dollars!" is correct.
Insert exclamation marks inside quotation marks if quoting from another source such as a magazine or book excerpt. However, if you have added the exclamation mark due to your surprise at the content of the quote, place it outside of the quotation marks to show that the original author did not express the quote in a surprised or threatening manner.
Express sarcastic or ironic humor by placing exclamation marks at the end of sentences. For instance, you can write, "Nice weather we're having!" if there has been heavy rain for several days or write, "Good work, genius!" if someone has done something stupid.
Avoid using exclamation marks excessively or they will cease to have any clear meaning. Many people send text messages and emails with exclamation marks after every few sentences, such as "How are you doing!", "I'll see you on Thursday", "Let's have lunch tomorrow!". This dilutes the meaning of punctuation and makes it difficult to detect surprise. Using multiple exclamation marks is also unnecessary; one will suffice to express your tone.