ADHD

Only way I manage it is to use my phone or something that I have with my all the time anyway. And the planner / to-do / calendar or whatever has to be right on the front of my screen so it's not an app I have to go check, it's just visible all the time.

Adding stuff is hard, until you get into the habit where it becomes pretty automatic (as long as your planner/phone is always right at hand - if I walk away thinking "I'll add that in later", I won't.)

My one tip is to put everything in it to begin with, it's more effort but it gets you in the habit quicker. So if you a morning routine, you can have "make coffee / brush teeth / read lemmy" as three separate tasks, and complete them all quickly. Or if random thoughts pop into your head during the day stick them on ("put a spare USB cable in my bag / Google terrapins"). Not only does it help me remember to do stuff, but it stops rando tasks distracting me. If I feel it's really important to check how much laundry detergent I have left, I can add a task, not stop in the middle of cooking somehting and rush off, only to come back and find dinner burnt.

For me, to-do lists work much better if I have to add and complete dozens of tasks a day. Because then it's something that feels like it's working and helpful, while if it's just "remember to do that big scary important thing" it just stresses me out and I ignore it. Obviously, ymmv, and some people find having lots of tasks distracting or hard to sort (or go down the rabbit hole of categories and color codes). But if it's something that I get regular dopamine hits from (by completing many small goals) I pay attention to it, while if it's something that just makes me anxious or feel guilty I won't.