While that is a tough question, there in my family is a general way it goes.You can't spend an entire day lecturing your child, because as others have said, they aren't going to process it.
But, you do need to discuss what they have done wrong.
The big thing is, you can't be the dominant one in the discussion. You need to get their feedback as well as you go along. Ask them why they're in trouble, what they did wrong, how they can improve it. Etc.
Personally, they do need to learn from what they did wrong, but if that method doesn't work, and repeated incidents are occuring. Then you may need to take it up a notch to discipline.
In my family we end the lecture with (before the hug =]) telling them what will happen if this occurs again. Such as, if they push their brother again, you will not be able to watch TV for a whole day. That is just an example.
Hope that this advice helps, best of luck to you and your family.