

Un-medicated adult with ADHD here.
Every case can be different.
First thing I wish I could have done:
find a therapist who specializes working with ADHD. they will help develop skills and coping mechanisms that will help them throughout the life; whether or not you decide to medicate.
Second thing:
Find them an active outlet, a high energy activity that requires focus. For me it was hockey, but I wish it was circus. Juggling helps me manage my ADHD more than anything.
Third: Help them develop routines in their life, when to eat lunch, how to get ready for bed, seems simple but it is the thing I struggle with most as an adult.
Finally I cannot stress the first point enough. Find a therapist that specializes in ADHD.
It’s not stupid,
If you can afford get a therapist, helped me more than any suggestion I’ve seen on this post.
May also work for you