Both answers above are correct. And as Bitsycabana said, it is important to make sure
the ADHD person is actually receiving and responding to the information you are sending to him/her. One way you can do this is by looking directly into the eyes and respectfully asking him/her to repeat back to you what you just went over.
Very important, though is to be respectful. We ADHD are already way down on ourselves, we don't need more pressure which creates anxiety and puts us into a downward spiral and depression. That is where mine goes. I am far harder on myself than anyone else could ever be.
Also, if a list is written, make sure the ADHD person has put it in a pocket on their person. Things need to be made habit. Not easy, but can be done. Same place for list
every time. Then it's always available at the store.
Color code things on lists, in house, so they are easier to relate to and find.