Practice serendipity (finding valuable and agreeable things when not particularly seeking them) - having a wide attention span and range of interests is important.
When we're involved in trying to solve a problem we tend to have a narrow focus but we should always be open and aware of the unexpected. What may seem irrelevant at first could later become significant in creative thinking.
It may take a while,perhaps weeks,months or even years, which is why the creative thinker should retain as much information and as many experiences as possible. It's these experiences that may be the trigger to a creative thought which might just solve a difficult problem