Responsibility is a wonderful attribute to have in a child, teenager, adult, employee, employer, you name it! Already when your children are young, you can assign them chores to demonstrate that members of a family work together to maintain the home and that Mommy is not the cleaning woman. In addition, responsibility begets maturity and increases self-esteem, as the child recognizes that he or she is a capable person.
Your teens should be responsible for their homework, their own room, and for cleaning up after their own projects. Once they have assumed responsibility for their possessions, you can look at your family circumstances and evaluate what additional responsibilities your teens can take on for their own growth as well as for the smoother functioning of the house. Usually, teenagers should be able to carry out whatever chores they're given just as well as an adult, although they may need a training period.
In addition, teenagers should be held responsible for their actions. If they lose something through carelessness, they should pay for a replacement or work to earn money to pay for it. If they forget an appointment, they should be the ones to call, apologize and reschedule. A parent who always protects a teenager from experiencing the consequences of his or her behavior is blocking the development of responsibility.
Most teenagers are capable of watching their younger siblings and may even babysit for other families for pay. In general, anything your teens get paid to do for other families (mowing the grass, shoveling snow, washing dishes) they can also do for their own family. Of course, the presentation is crucial, as you don't want to come across heavy-handed or as if you're enslaving them. If your teenager is bogged down with homework or finals, however, schoolwork is a primary responsibility, so you might want to scale down your requests until the busy academic season passes.