My boyfriend has ADHD and he thinks that there is no natural remedy to it. He says don't give Ritalin as he hated it. (which you wont anyway, so don't think it applies anyway).
Signs for him were constantly active, cant focus on just one thing for very long, can be very short tempered, which can lead to physical aggression and general unrulyness, like being daft and giggly for no reason. As an adult he is more controlled, so I don't really know much about what he was like as a kid apart from being told by his mum.
He was in school when diagnosed with it.