RTB, I'm not a ya teacher, but I can tell you which teachers have been most effective and why.
One was excellent. He placed emphasis on worship and on teaching us to be witnesses, to be the ones most active in the church and leaders in getting things going. We learned different ways of presenting the gospel story, and he encouraged us to find situations where we would be able to do so. He also taught us how to be examples for our teens in the church and our own children, and often brought in lessons on family, how to keep our marriages together and how to be good partners.
We learned, we shared ideas, we all participated in the discussions, but he didn't let people take over the discussions, although he never discounted a single persons ideas.
On to a not-so-great teacher. He wanted to teach, but I think he thought he was still teaching kindergarten kids, and the people in the class reacted by acting like kindergarten kids. They talked, joked, he didn't have leadership skills to direct the class in the right way so that this wouldn't happen. The result? Nobody was growing, nobody was learning much of anything.
A good lesson will be contain enough that new Christians can learn, but go into enough depth that people who have grown more can also learn new things too.
Look at the class, get an idea of where everyone is in their lives, and target a few things that need to be worked on overall. As in, if you see marriages are dissolving, focus more on teaching biblical principles that make strong families, if the majority lacks basic knowledge of why they believe what they do, focus more on that. Don't be afraid to start out by passing out a questionairre they can all answer anonymously so you can get an idea of where everyone is, and have them put down ideas for what they think would be helpful.
Gina