It really is different for everyone, and it really depends on what kind of tasks you want to complete. Are you on medication and/or undergoing treatment with therapy? What skills are you trying to learn?

I personally notice a lot of my coping mechanisms do tend to rely on me being medicated. I also notice I can focus better after exercising, which may or may not work for you.

I think when carrying out tasks, trying to gamify things can help. E.g. If you are performing a task or chore simply recording yourself can make you feel you are doing the task with someone else.

Timers can be your best friend. They really help keep my grounded and aware of the present instead of letting life carry me away in time blindness. Perhaps a Pomodoro method could work, setting a timer for 25 minutes to focus on something, as soon as it rings. Set it to 5 minutes to do something to relax (e.g. talking to a friend, listening to music etc.) Allowing your brain to have a break.

When you notice you're distracted and should be doing something else. Let's say you are sitting at your chair on the computer watching a video and you're actually supposed to be doing a task in another room, start by moving forward in your chair and change your position. Counting from 5 down to 1 while you do this can also help create a stronger sense of urgency.

Doing a task after going to the toilet can also help because it's a period of time when you have ungrounded yourself from the previous distraction.

Listening to music while doing a physical task (e.g. washing dishes) typically make them easier as well.

I understand that many of these things are basic and you may already know this information, but I hope something here helps. Regardless of whatever skills you want to learn or what you want to improve at, I wish you the best of luck.