I strongly disagree with the 2nd poster. You set reasonable limits. You set an organized schedule..same thing everyday, same time. You encourage, you praise..you find things they are successful at so they can build self-esteem. Use a chip/reward system to reinforce appropriate behavior. Yes, I've been there.
My 8 year old has ADHD and I don't think that a schedule is the answer at all. I agree with Loa1002. However, I'd concentrate on adding OMega-3s. I have done my best to teach her appropriate behavior and she is doing well now.