Discipline is never easy, yet it is necessary when it comes to providing the right guidelines when rules have been crossed in a parent/child relationship. It can be hard to exact discipline when you're dealing with an aggressive teenager who has little or no respect for rules as is. How then can a person in authority administer discipline and reach the heart of those teens who are a bit more aggressive?
The first step is realizing that you can't discipline each teenager the same way. Each have unique personalities and situations, so what works with one might not work with another. Approach the teen with the goal of addressing their specific need at the moment.
Pick and choose your battles. Deal with the immediate problem at hand. Don't take this moment to touch on every situation "you" feel needs handled, frustrating the teenager even more. It's not about raking the teenager through the coals to get your point across, it's about reaching their heart so the discipline administered will not fuel their anger.
Make it a point of talking with the teenager on neutral grounds. Teenagers certainly need discipline which moves them on to being responsible adults, but a teenager who is aggressive might not be so willing to respond, in a positive way, if you try to discipline in a place they consider their own or that is public to others vision and ears.
Try to remember the emotions which raged through you as a teenager. Being a teenager is right in the middle of leaving youth and growing on to maturity, so the conflicts which arise often times fuels aggression, leaving the teen not fully understanding why they rage the way they do.
Teenagers aren't as free with talking about what upsets them these days. As a parent/guardian or person in authority this can leave you feeling frustrated, but you never truly know what is going on in their life, everything is tragic and traumatic. Try to approach your teen with this thought in mind. Give them the opportunity to open up to you, but on their terms.
Be willing to acknowledge their feelings and views without compromising your rules. Let them have their say, no matter how much you want to put a stop to what is being said. It takes two ears to listen and a heart to discern. If you are willing to give the teen the freedom of expressing their grievances, of course with mildness, (you'll need to stipulate that you're willing to listen if they don't yell or shout and you follow through by listening), you'll be surprise how much they'll appreciate this and how less aggressive they'll be.
Discipline has to be meted out according to what circumstances you are facing with the teen. It isn't going to be easy no matter the way you approach it, but if you do with gentleness, mildness, and a listening ear, the door might remain open so that the teens' heart is reached.
The whole point of discipline is to steer that person/teen away from a bad course which could bring about harmful results. Finding a common ground to approach an aggressive teen on is important. Allow yourself to be vulnerable and impart pass experiences which might have set you on a wrong course if you, yourself, hadn't been disciplined. This allows for those toeholds in a teens life which might help to break down those walls of aggression.