Punishing is a balancing act because you still want to be a good parent, don't want your teen to hate your guts, and you don't want to be Hitler.
Options and choosing
What you must remember is that your teen is becoming an adult, therefore it's your job to help her make the transition. One way that you can help them make this transition is to start letting them choose what will happen to them if they do not follow the rules.
Give your teen options and a chance to choose what he wants to do. When you do this it allows your teen to feel like he has a little bit more say or freedom in his live. Yet it allows you, as the parent, to still maintain control of the situation. The catch is that when you give your teen options you must also give very clear rules and consequences with those choices.
Set clear rules and consequences
Give your teen two choices that very clearly state what she can or cannot do. Teachers use this method all the time in what's called classroom management. Here's an example that can be found constantly in classrooms, "You can put your cell phone away right now or I will put it on my desk where you can pick it up at the end of school." The teacher allows the student to choose what will happen to their cell phone. It's respectful, gives some power to the student, allows the teacher to maintain control of the situation, all while allowing the student to feel in charge.
So with your teen and, let's say, curfew you could say something like, "Zack, you can either come home tonight at 10 p.m. after you have shown me that you are done with your school project or you can stay home tonight, finish your school project and wash the dog." Remember, consequences don't always have to be negative they can be positive.
No gray lines
When you set the choices and consequences with your teen, make sure there are no gray areas when it comes to what will happen - positive or negative. Teens are notorious for telling their parents that they always change the rules to try and corner them when they are in trouble. If that is your teen, something you might try is literally writing out the choices and consequences and posting them on the fridge (or wall, etc). That way when your teen tries to weasel his way out of a sticky situation, you have it all in writing.
Parents, this is extremely important as I am sure you already know. If you want your teen to be responsible, and actually make decisions well, then you must follow through on what you say you will do. My mother would always threaten to throw my brother and me in time out when she caught us fighting. Here's the thing though, it never happened. So when my mom yelled, "I'll put you two in the corner if you don't knock it off!" we laughed. She never followed through, so it just became a joke.
When your teen follows the rules it's important for you to reward properly. You, as the parent, need to show them that when they respect your wishes you are willing to give them more respect. If you set a curfew for your teen and she follows through, try giving her a reward like adding five to 10 minutes to her original curfew. But if she breaks curfew, go back to the original curfew. You may find yourself changing rewards as fast as the tide changes, but when you reward properly your teen is more open to following the rules.
Being a parent isn't easy and punishing or disciplining isn't fun. But with these few steps you will be able to find a way to effectively punish your teen and help him make the transition into a proper adult.