One of the worst ways to start a story is by opening with characters screaming and yelling at each other in the dialog.

It’s grating to start a story in the middle of an argument, and it’s jarring to open in a war zone of words.  Imagine walking into building for the first time, and having someone shouting angrily.  You wouldn’t want to be there, would you?  Opening with a whining or screaming dialog is basically greeting the reader in the same way.

If there are exclamation points and capitalized words in the first paragraph, you’re doing something wrong.