Excerpt from an article in ADDitude magazine.
To avoid parent-child power struggles, make fewer verbal demands. Instead of telling your child what to do (which is often perceived as nagging), use a nonverbal cue. “Children with ADHD may lock into certain behaviors and lose focus, but parents can often redirect them with a simple nonverbal cue,” says Lynne Reeves Griffin, author of Negotiation Generation: Take Back Your Parental Authority Without Punishment! Griffin suggests handing your child a sharpened pencil or lightly tapping your finger on his worksheet when he is distracted. “When parents use nonverbal feedback, it helps children get focused quickly. This is encouraging to a child who is struggling,” Griffin says.
When your child does something that helps the evening go more smoothly, acknowledge his contribution. Children feel valued when their actions are appreciated. Using phrases like, “Thanks for your help” or “I appreciate your cooperation,” makes a child feel good about himself.