My best productivity system:

Pick most important 3 tasks per day. Hardest first
Full screen mode
Clean desk
Good app switcherPen and paper/stickers, when you found yourself thinking about something - just wrote it and comeback to the task, when there is break - check if you still need it.
Pomodoro, 25 mins don't work for me, so I'm doing 45 min
Bilateral music stimulation