The best punishments for teens are the ones that get them to think about what they did and then to realize why they shouldn't do it again. Punishments that "fit the crime" are designed to give this awareness. For example, if your teenager stole money, an appropriate punishment is to return the money or to work to earn money, which is then repaid. If, despite punishment, the misbehavior continues, parents have to become detectives to uncover the underlying reason. Unfortunately, the diagnosis could be that the teenager is stealing to support a drug habit, to "steal" love that he or she feels is lacking, to alleviate pain from emotional or physical abuse, or because he's afflicted with kleptomania. Once the underlying cause is dealt with, the stealing should stop.
A teenager who habitually comes home after curfew can be grounded but be sure not to give out punishments for an extreme length of time. If staying at home after school for a week teaches teenagers that they have to be responsible about time, three or four months of that punishment is excessive. Your teens should always know that you're giving them a natural consequence of their behavior due to your love and concern and not out of vindictiveness. Explain that it's dangerous to be out so late at night, that he or she will be unable to get up in time for school the next day, or whatever other reasons you have for not allowing the behavior. Let your teens see that you want them to have more independence as long as they can handle it responsibly.
Try not to focus too much on punishments; rather, try to encourage a home atmosphere in which communication, explanation, negotiation, and compromise predominate. It might be more work than laying down the law and punishing, but it prepares teenagers for life in the real world when they'll have to make their own decisions and not rely on their parents to police them.