Create a quiet space for them to learn with no distractions.
Give them something to fiddle with whilst you are talking to them or you want them to focus. It can also be helpful to let them move around whilst they listen.
Ask them to do one task at a time
Provide checklists or visual timetables to support organisation.
Use timers to help with time management and build in frequent movement breaks.
Suggest rather than criticise (children with ADHD often have low self-esteem)
Provide lots of opportunities for exercise and movement.
Set up a reward scheme to encourage them and support them with their behaviour.
Build on success and help children to pursue more of what they enjoy.