Leading teens is different than leading children and older adults. Your role is more about leading them into maturity and teaching them about adult responsibilities. Teens are better able to handle responsibilities and understand what's expected.
However, for many older adults it seems daunting to lead teens since they have a reputation for being rebellious. What if they don't listen? What if they "walk all over you"? Here are some tips that may help you to lead teens.
With teens, it's important to respect their place in the leadership process. (This is important with all ages, but teens are more aware of their own independence.) So remember that you can't be a leader without followers! The teens have to be there for the leadership to happen.
As noted above, respecting those you lead is important. Teens may not respond well to just being given orders; it's more than that. One way you can show your respect to the youths in your charge is to listen to them. Really hear them, and respond respectfully to what they say. This not only shows your respect for them; it also sets a respectful tone in your group, and in so doing you're leading by example.
Because you're modeling it, this shouldn't be too hard to enforce. Ask that your teens treat each other with respect, and you can cite yourself as an example.
Teens have a pretty good sense of when something or someone is faking it. The teens in your charge are not looking for perfection; they would much rather connect with someone whose flaws they can identify with than someone distant and aloof. That said, it's important to guard against hypocrisy - for example, it's okay to be real and share that you used to be a smoker while advocating that your teens not smoke; but if you are still smoking, your words will ring hollow.
Leading teens means assuming the role of a mentor. Mentoring means setting up an environment where learning takes place, and being available for teaching and answering questions. In an effective leadership relationship with teens, it's important to know when to step off and let the teen try on his or her own and when to step in. If you have a good relationship with your teens, then you will likely know them well enough to discern when to get involved and when to back off.