1. Seek God's guidance for your child(ren).
Understand that your children have been entrusted to you by God, and seek HIS guidance in raising them, etc.
2. Know your spiritual gifts and expose your child(ren) to others who possess various different spiritual gifts.
God has gifted each of us uniquely for our walk, and HIS plan for us. You will have come gifts that you can encourage and disciple in, but we are certainly not strong in all areas. A balanced discipleship path for your teen is to expose them to believers with other gifts to help them become well-balanced and mature in their faith.
3. When in doubt, start with the basics.
At a loss with where you should start? Have you considered teaching your child(ren) about prayer, Bible study, Scripture memory, witnessing, ministry, worship and fellowship? Have you taught them how to study the Word? Do they have a mentor or disciple in their life other than you? Pray for/about this, and seek to pour the basics of the faith into them so they can grow in Christ!