I recently wrote up a step by step outline to help Christian parents respond to the sins of their children in a way that takes them to the Cross and makes it a positive opportunity to praise Jesus' grace vs. a fight for mere behavior modification. I hope you find it helpful.
Bringing the gospel to bear on your child’s heart
A. When your child is not sinning
1. Thank God for giving him ‘obeying grace’.
2. Praise him and help him praise God for ‘obeying grace’.
3. Enjoy who God has uniquely made him, and don’t mistake immaturity for sin.
B. When your child is sinning
1. Control your reaction. Be calm and don’t be surprised by his sin.
2. Go to him and tell him that you need to meet with him privately.
3. Engage with the positive/hopeful attitude that this is a gospel opportunity.
4. Gently point out his sin. Use the Bible and be as specific as possible.
5. Help him understand that his sin offends God and hurts others and himself.
6. Help him feel the pain of his sin via corporal discipline or some other ‘pain’.
7. Help him understand his natural inability to please God without saving grace.
8. Pray with him (him praying too) with words of hope in Christ’s kind grace.
9. Do not harbor the incident in your heart or bring it up ever again. It is forgiven.
10. Thank God for your child often and enjoy the evidences of God’s grace in his life.