Age 2 to 3: Civilization Dawns
At this stage, they're still operating with limited self-control, but at around 36 months, new and stronger brain activity helps improve memory, language and impulse control.
Take action. You can't expect your child to have good manners without your help. So if she has taken another kid's toy at the playground, step in and insist she return it, informing her that if she doesn't, there will be consequences. And don't say, "I'd really like you to think about giving the toy back." It's too much to expect a child to make that decision. The fact is, she doesn't have a choice in the matter, and she has to know that.
Next: Age 3 to 5: Progress, not perfection