Start with a question, draw the nodes, refine the nodes and do it over and over again, then the patterns emerged and get clarity and you can answer the question.
First, start with the draw. The draw helps understanding the system.
After the sketch is done, use the cards or sticky notes. These can be
moved around and now you can discover new relations.
The third part of the exercise is to draw but in a group. Now everything can be discussed, questioned and after doing many iterations we can have a deeper understanding of the problem and eventually find a solution.
There was a contradiction during the talk, on one hand he stated that the conversation are important, and on the other hand, the practice tells that if the team is doing the exercise in complete silence, the group do it better and quickly(at minute 4:26).
Source: Got a wicked problem? First, tell me how you make toast by Tom Wujec