That's not gonna prevent them from being spoiled brats. Simply avoiding giving your kids what they want in an attempt to shut them up, and rewarding them when they actually behave is a step in the right direction though. In other words, make sure that their path to the reward doesn't involve any bratty behavior.
And as for punishments, not giving them a reward really is punishment enough. It's better to have them realize that they won't benefit from bad behavior than it is to have them fear making demands (as some of them may be warranted).