This is harsh, and I totally admit it, but it worked. I told my son if I counted to 5 and made it to 5 he would get a spanking and then go to bed, and he wouldn't be able to come out of his room until he had slept. He's only been spanked 3 maybe 4 times. Now I only have to start counting and he's totally in line. After he comes around we talk about the issue. That's for extreme behavior issues, like violence.
For not extreme behavior issues we have a goal and reward system in place. That works well for general defiant behavior and transition issues. My son comes up with his own rewards, and I remind him (sometimes way more than I want to) of when his behavior is moving toward a negative consequence, and what he will be giving up if doesn't come around.
A method that worked for us with both boys...Look her in the eye, tell her it isn't acceptable and she can't get up until she calms down. Put her back in time out. She knows it's wrong or she wouldn't do it. Don't engage her except to repeat that she need to calm down. Just keep putting her back in time out no matter how many times you have to do it, no matter if it takes all day, and no matter how exausted you are with it. It is no easy. Eventually she will know you mean business. (I hope)the nice thing about 6 y/o's is that we are bigger than they are. So if my child spit, kicked or hit me I would pick him/her up by the arms or the waist- hold her/him out from me and tell him "no- you will not do that to anyone" and I would put him in the bathroom with the door closed for 6 minutes. If the screaming didn't stop or he came out- another 6 minutes. If you are are consistant it will only take a week for the behavior to change. I know this sounds harsh but I have to tell you this technique was used when all else failed!!! No success with any of the traditional methods. Having a child with ADHD/ODD and sometimes physically aggressive outbursts led us to seek counseling. One of the Psychologist's said send him to his room for the day in pajamas no matter what time of the day it is. Did it two Saturday's in a row for hitting his cousin .So this method didn't work. The next Psychologist recommended us putting him down on the floor face first with arms stretched out. He stressed that both parents are to be present so the child will not associate one parent being the bad guy and he would understand that we meant business. One parent straddle him with your knees on both sides of him(don't put your weight on him) and place your hands over his arms so he can't move. The other parent is backup in case he starts kicking(which he did) or to touch the straddling parent's shoulder as a signal to see if they need to switch places or if you think they are holding arms to tightly. Place egg times to 6 min. near him so he can hear it ticking. Do not engage him in conversation or let his cries for tissue, toilet, or anything stop you from continuing to restrain him for the entire six minutes.He was not physically hurt by any of this. We have done this 3 times. The first time we did this I was so close to giving in but I knew that him being so little & aggressive at this age that when he gets bigger this might be impossible. The Dr. also told us not to do this in front of anyone else because they would not understand. It really helped with his aggression to our little weiner dog. He was constantly every day sitting on him, pulling his ears, or some kind of torture.I was about ready to find a new home for this old family pet because I could not control my 5 yr old???? The dog has been in family 13yrs. Please know that we feel like we finally have power over him! We have had power struggles with this child since he started walking at 11 months old . We still have issues with him being defiant but not for being physically aggressive. I know you may not even consider this but I had to tell you what worked for us. Good luck! Also we have a poster board with rules on it and he knows what the consequenses are if broken.The aggressive ones are spelled out hitting,kicking, spitting, punching, or getting in someones face and acting like going to hit.When my youngest was 8 and getting aggressive/violent, we added hitting, etc to the marble system (see top thread of this board). This was in combination with the right meds and a different way to deal with the scary violent tantrums she was having. For tantrums, we had a series of things that we did that reduced the frequency and length of time in a tantrum. When things were calm I would tell her that her room was a safe place to calm down (as is any time out place), and that when she was calm enough to talk, we could solve the problem. As soon as she gained any sort of calm we would praise heavily and help solve the problem. We made sure to let her have her way when being pleasent and calm and pointing out the benefit (to her of cooperation and discussion). A 6 year old may be too young for some of these tactics, but keep them in mind as time moves on. Our now 12 year old is doing great now and is pleasent most of the time and can stop to work out a problem rather than just react badly. It has been a journey but is worth it. Keep trying things until you find the one that works for your situation.