Pretty simple concept, I think. Exclamation points are used to add emphasis to sentences, phrases, and even individual words.
With a declaration: I can’t believe you put an exclamation point there!
With a command: Put a period there now!
With an interjection: Wait! Don’t put an exclamation point at the end of that sentence.
Overuse of exclamation marks causes them to lose their value. So, don’t be like Elaine. Mr. Lippman won’t be happy.
