Be a role model:
All you need is to set an example for them. Kids are just like robots as they always idealise and follow their mentors. So it’s you who will guide them to right path. Instead of yelling at them, be polite to other family members in front of them and then tell them why it is important.
Appreciation and reward:
Do appreciate them if they are trying to follow your instructions. You may introduce a chart where they will get a “star” for doing one good thing. Give them proper reward if they touch a certain level of improvement.
There is no shortcut to experience so let your kids see the real shades of life. Let them have real experiences for example if your child beats his friend let him face the consequences as it will be a great lesson about social behaviour.
Look for the root cause:
Instead of taking “disciplinary actions”, get to the basics. You should know the real cause of your kid’s behaviour as it will suggest you some proper remedy.
You must come at their level before offering them some piece of advice. They will feel confident to share anything with you and ultimately you will be able to correct them.