Meds. Everyone reacts to different meds differently so not all ADHD meds have the same (positive) effect for everyone. For me, Concerta works super well, but it might be something else for others.

Aside from meds, a routine works wonders. A routine with all of the day to day activities happening in the same order at roughly the same time (such as taking meds, doing the dishes, cooking, walking and feeding the dog, going to bed/getting up in the morning, etc). Or on the same day every week (such as cleaning, laundry, grocery shopping, etc). If I need to add something to my routine it takes some time to adjust, so I preferably only add one thing at a time and other activities within my routine may get a bit chaotic for a while but as long as I stick to it it’ll eventually become part of my routine.

The only downside to this is: if anything is different from my usual routine (it could be something as simple as the order of activities changing) it might mess up the routine for the rest of the day…