I am not sure I can have any affect on when I will have ideas. They show up at the strangest times. Never when you are sitting solely trying to think of something. I agree with what most of you have said, many times while I am washing up or laying awake at night trying to go to sleep. When I am out walking around things often come to my mind. If I am content it's difficult but if I am going through a hard time it becomes easier.