This is how you show emphasis, for all of you who got dropped on your heads.
The above sentence has several examples of how emphasis can be shown.
1. Italics
2. Exclamation points
You wanna know what is not correct, and makes my eyes bleed every time I see it?
"NO!" she cried. "DON'T LEAVE!"
That, right there, will make me set the book down faster than you can say "I'm a terrible writer who doesn't know how to emphasize correctly."
You should never—fucking never—use capitalized letters to show emphasis. It is one of the most painful, most unprofessional things I have ever seen in my life and it shows me that you obviously do not know what the hell you're doing on the damn keyboard and that you should probably get off and never come back.
You use italics or exclamation points. Don't use them too close together, don't use them to emphasize stupid things, and don't use them to make yourself look cool. Because it won't. Trust me.
DO use them to: Show when a character is thinking, show a flash-back, show unique terms, show books within the story, and show how smart you are that you know when to use them correctly.
But please, don't over-show emphasis. That sentence up there is not fully correct. If you're using italics, then I'm sure the audience will get the point and you won't need exclamation points.