I am always being asked for the best productivity and time management techniques. There is no one answer: different methods work for different people. Also it is common for those affected by ADHD to get bored with a system after awhile even if works well for them. This means we always need to be collecting new ways of doing things that work for us.
One method popular with those affected by ADHD is the Pomodoro Technique. Invented by Francesco Cirillo in the late 1890s, this technique uses a timer to work in intervals of 25 minutes. Between each 25 minute interval a three to five minute break is taken. After four intervals a longer break of 15 to 30 minutes is taken. It is important to choose the task you are going to undertake before starting the timer so that you are on task during the full 25 minute interval. Track the intervals, maybe with a check mark on a piece of paper, so you know when you have done four intervals and can take a longer break.
It is also helpful to track what you did during each interval so that you begin to learn how long in takes you to accomplish certain tasks. Many of those affected by ADHD have little sense of how long different tasks take even if they are tasks they do often. This can be helpful information in planning your day and what you plan to accomplish.
As for the name, pomodoro means tomato in Italian. The timer that Cirillo used while at university was shaped like a tomato. So we have the Pomodoro Technique.