Second, the group has to trust in the Word of God. Ideally speaking again, that trust would be created by loving Christian parents. Find a youth group with only children of church members, and you find one that is not living up to its potential. Once again, this may fall back on you. Trust in the Lord's Word will not come from outings to the movies, concerts, and softball games.
Teens have to see it, live it, and want it.
A group that has a healthy balance of worship, prayer, study, service, and fun will bring trust to both the Lord and you. Last and most influentual, the members must trust each other. This last step is sometimes the most difficult simply because we cannot directly control it. We can take steps to help it thrive, but only the individuals can create trust among themselves. Let them know it doesn't happen within the group and take steps to enforce it if need-be.