The age-old phrase "Actions speak louder than words," is true. What you show your children by way of your behavior is often more important than what you say. In the social work field, we call it "modeling behavior". If you don't want your child to scream and yell when they get upset, you must first ask yourself if you would be calm in the same situation. To ask our kids to behave differently (or more appropriately) than us is not only unrealistic. It's hypocritical.
I believe that the Golden Rule offers some brilliant advice as it teaches us to treat others the way that we want to be treated. You might remix it this way as you look to help your child behave positively... "Act the way that you would like others to act".