The Power of Friends
Once they're in preschool, children can find a buddy without much encouragement from you. "That's the magical year when most are ready to enjoy the company of another child. Sometimes they'll choose a friend based on similar interests or because they laugh at the same things," says Wallace. "They also may choose friends who have different personalities -- who are wilder or braver than they are."
It's hard to predict which of these early relationships will last longer than a school year, but the chances are better with support from both sets of parents. An enjoyable outing with that child's whole family can strengthen the bond even more.
But it's also common for even an intense friendship to fade at this age. For most kids, relationships tend to change as they develop new interests.
Throughout this period, you can continue to teach your preschooler ways to solve his dilemmas, but you'll have to set the limits during playtime. You might come up with ground rules with the friend's parent in advance, so that everyone is on the same page. Rules might involve what kind of consequence to impose for aggressive behavior or even which types of games are off-limits. But if you haven't done this, it's okay to invoke your house rules as long as you aren't heavy-handed. Usually, all you need to say is "We don't allow that in this house."
You can also prompt the kids to come up with their own solutions. "You might say, 'I see we have only one ball and two kids -- what should we do about that?'" says Wallace. "Very often, they'll come up with a way to take turns or even introduce some other toy to the situation."