Are your parents yelling at you? Don't worry. Remain calm. Just read this article.

[edit] Steps

Acknowledge that you might have done something wrong. Even though you might not think so, look at it from your parent's point of view. Maybe they do not understand why you have done whatever they are mad about.
Don't back talk. The urge to snap back at your parents while they are yelling can be almost unbearable, but don't do it. This will only make them angrier and make the situation worse. Keep your comments to yourself. Another great way is to continually say "yes mother".
Remain calm. Don't get angry. More anger is not what the situation needs. Instead, take a few deep breaths. Regain control of yourself.
Attempt to explain the situation from your point of view. Be polite and apologize. Be sincere, even if you don't think you did anything wrong.
Above all, remember - everybody's parents get mad at them every once in awhile. It's not the end of the world. Understand that your parents are just doing the best they can because they love you.
Don't mimic them even if you think your out of earshot.
Don't concentrate on the conversation, keep your eyes fixed on the parent but use your peripheral vision.

[edit] Tips

Try not to repeat the behavior that set off the screaming.
Remain calm.
Be polite and respectful.
Don't back chat (too much effort really)
If the situation calls for it, a good comment is "It's not the scars you can see that hurt the most" (that one always makes them bewildered and scoff but they never have much of a comeback to that one)