Your child lives in a very complicated social world. This has always been true for children: all parents can remember their own tears or rage at the cruelty of another child; all parents can remember wanting desperately to be accepted and approved of by other kids. Most of us can remember, at some point in our lives, longing for a best friend.

Things are even more complicated for children now, as media has introduced children to the world of adult mores before they are emotionally ready. Our children do not know, just instinctively, how to build good relationships with other children in such a culture of shifting rules.

Luckily, healthy kids generally make healthy choices even in the context of difficult peer situations. That means that if children have good relationships at home they have a healthy head start, but they still need your help in learning to navigate a complex social world. Some basics on how to help kids develop the social skills they need:

1. Foster good social skills from toddlerhood on. This is one of the most important skill sets your child will ever develop. It is infinitely more important to her future happiness than helping her develop her intellect.
2.  Support his friendships. Honor and reinforce your child's developing friendships. Talk about them, remember them, create opportunities to play. Remember that children get aggravated with each other, just as adults do. It doesn't mean the end of a friendship, necessarily, just that they need help to work through the issues that come up.
3.  Model respectful relating. Remember that your child will treat others as you treat her. In addition to the obvious everyday respect, that means that you give her criticism in private, not in front of others, including her friends. Which means you have to find tactful ways to talk to your young child and other kids about the way they are treating each other, to help them work out difficulties when they play together.
4.  Teach your child that people are important. All parents have to choose their battles, so put up with messiness and dawdling if you must, but teach your child consideration for others. Model it for him early on, praise it, help him brainstorm to solve peer problems, and don't let your child intentionally or unintentionally disrespect another person. It you can't confront it as it happens without embarrassing your child, be sure to talk about it later. As kids get older, you may need to be very explicit about insisting that they acknowledge adults in their presence, as well as other kids. Often preteens and young adolescents need to be reminded of this, and to be given coaching on how to handle interactions that feel awkward to them.
5.  Teach kids to express their needs and wants without attacking the other person. For instance:   

• "I don't like it when you push in front of me like that" instead of "You're mean!"
•   "I need a turn, too!" instead of "You're hogging the ball.
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Help your child learn how to repair rifts in relationships. 

When we think about repairing relationships, we usually focus on apologizing. But premature apologies won’t be heartfelt and may backfire by causing the child to hold a grudge. Giving them a chance to cool down first always works better. Apologizing is a very useful friendship skill that doesn’t come easily to people in our culture, mostly because we feel like it indicates that we are bad or wrong for making a mistake, to begin with. But all human relationships will have conflict, and kids are still learning how to handle conflict. So be sure not to make apologies into public shaming, or your child will always resist them. And be sure that you're modeling apologies. 

If you never apologize, they won’t either. If you apologize graciously and often, to them and to others, they will too. The secret of helping kids learn to apologize is not making the apology into a punishment.

Source: https://www.ahaparenting.com/parenting-tools/socially-intelligent