A great pass training exercise by Pep Guardiola at Bayern Munchen.
I did this exercise with the U12 (regional) youth players as a warm up, and it worked well in two phases. First, I split it up in two separate groups, each doing the same, simple exercise (left on the picture).
Secondly, I started with everybody together with one ball: good coaching is important there. When this went well, we tried two balls, each starting at 'player 1'. In the beginning, I paused the exercise after every succesful run (means 3 passes, so the ball is with players 4), so the players would move correctly to their next position (actually, just following the ball).