In his book ‘The back of the napkin’ Dan Roam explains the process of visual thinking. The core of visual thinking is an iterative process of looking and seeing (as visualised on the left on the photo underneath). At first you need to look at a situation from different perspectives (Who/What, How much, Where, When, How and Why). By visualising these perspectives, gaps within the story show up (you will actually see it) and imagination can help to find solutions to the problem.
When you’re done analyzing, imagining and sketching you can translate it in a final visualisation to communicate your findings to others. The final visualisation you come up with depends on its purpose.