Kids have the tendency to be selfish that everything should be for himself. By action, the parents could teach the child slowly by sharing the food at first and later on the some things until the child learns how to share his toys. This is one difficult task but parents who neglect their child in this good behavior could raise a brat.
You're right. A brat or a kid usually displays the traits of being helpful and sharing a good service to everyone as what they have been taught by his parents.
What I've learned is that parents should always lead by example so that the kid will follow what he has seen.
Establishing good morals and ethics while they are still young is the best way to do it. Mould them while young, they say.
This is the current stage of my daugher now. Sometimes, she shares with her friends...other times, she's a bit bratty. Me and my wife are now working double-time to teach our daughter about generosity.
Encouraging sharing is the best way of teaching generosity to kids (adults too). There is a ton of research showing that being compassionate and generous extends one's life by releasing happiness endorphines to the brain.
Whatever we want the kids to learn, we must first ensure that that is exactly what we do and how we behave. Because after all, the kids learn by watching their parents. If we are being selfish and tend to hog everything without sharing, how can we tell our kids to share. The kids learn and adapt to behaving in a particular more by emulating others rather than be taught verbally.