D.M.
as a mother of 6 kids - you had better step up and get control now! They get much more defiant at 12 - 13 years old, so if you don't have control now, you will not have control then.
What you do NOT want is for them to turn their anger at being corrected to you, but to be sorry for what they did. Each child is different so you have to taylor the punishment to fit the infraction and the child.
Have consequences; if you do this, then this will happen (if you throw that ball at the TV again, I will take the ball away from you)
Mean what you say also. (if you don't stop screeming in the car, I will stop and put you outside)
Give them choices; you may have this or this (for a snack, you may have apple slices or a banana) let them begin learning to make wise decisions.
Sometime, you have to increase the consequences; 2 of my kids still were extremely stubborn and we had battles - spanking became necessary - but after the first time, rarely had to go there again. And I always spanked the butt with deliberate swats (listen for a change in their crying - and they will cry - there is a difference between "I'm mad at you for correcting me" to "I am sorry I did not listen") also not when I was so mad - you NEVER want to lose control of your own actions either (and some kids can push those buttons easier than others!)Keep your sense of humor! it is ok to put yourself in a "time out" if you are getting too frustrated.
I had a BIG flat wooden paddle that I usually just had to pop the counter with to get their attention; if the child thinks you mean business, they will respond. Kids live up to their expectations - but need firm boundaries that they will CONSTANTLY test. Stay strong!