* Have a calendar at hand everywhere -- on your computer, on your phone, everywhere. Enter stuff into it immediately. Live and die by the calendar, because you will never remember things on your own.
* Know what you're aiming to do on a day. Maybe you can cope with a to-do list, but speaking for myself they feel oppressive, like I am judging myself for all the things I've failed to do. But you can keep one thing in mind.
* Email yourself! I bat tasks back and forth between my home and work emails, based on where I can act on them.
* Exercise. It helps with a lot of things and research suggests it helps with ADHD as well.
* It's the morning. You've made coffee. You should be preparing to do some exercise. Don't open the laptop or phone. I know you're going to "just check". Don't. Don't start, you won't stop.
* When you learn about something that distracts you easily, either give up the addiction or accept the cost. I've pissed away thousands of hours of my life on websites like this one. I have mixed feelings about what I gained and lost. Right now I am noticing that Slack is becoming a problem for me.
* Read books. Physical books lack the ability to open tabs or follow links.
* Have times of day when you ignore things. At work I generally ignore messages on my phone. At home I ignore emails from work. In particular, there is no way for my work to reach me on my phone. No email, no slack, nothing.
* Work in pairs! This has been phenomenal for me.
* Do you take shorter-acting medication, like I do? Set an alarm for the doses you need later in the day. Left to my own devices I can easily sail past 2pm and then at 4pm wonder why the hellSQUIRREL I can't conCLANGcentrate on my wWIKIPEDIAork.
* You will struggle with impulse buys. Rehearse in your mind what it will be like when you get the thing. Think about the regret of having given into the impulse. Even a few seconds of delay can break it.
There are probably other coping mechanisms I don't realise are coping mechanisms.
These are not enough by themselves. Not even close. Almost every one of these is only possible because I am taking ritalin, and every one of them is necessary because ritalin can't do everything by itself.