I work daily with young kids and my daughter is ADHD as well as my brother and father --liebling's advice was very good - I found those tecniques worked well for me-
Remember you are the parent and you need to be in control of the situation, the child will act out if they sense you are not in control
You need to show them how to act and behave-you need to be calm, when I am stressed in my own life, I find my daughter acts out more
Lots of sleep (11-12 hours a night for the 6-10 year olds)
I would put my kids in bed at 7 and let them keep the light on for an hour or a half hour - they could read or draw but could not be out of bed or active or watching any tv or computer (the result was that now my kids love to read)
Lots of predictable routine at home and plenty of physical activity (sports, playground ect.) is very important
We signed up for this job - so now we need to give it our all while it matters, when they get to their teens it will be too late
good luck!