I used to depend on the pomodoro technique and a other hacks like "autofocus" etc.
Basically techniques that allow you to set targets that you can easily and provably reach even if that target is just work-on-this-and-nothing-else-for-x-minutes-and-make-a-check.
Edit: and deadlines. Maybe another reason why the pomodoro technique works so well.
I mentioned this in other comments on this thread but there is a video series that is really great by Russel Barkley - he talks about education and coping strategies for kids and adults that aren't totally reliant on on meds. Relying on lists and reminders are important for adults