Sportsmanship is always important, win or lose. A great resource for parents and coaches is the Positive Coaching Alliance, an organization that seeks to develop better athletes and better people through sports. If you coach, I highly recommend the Double Goal Coach certification: one goal is winning, but the second is developing character and sportsmanship.
PCA wants athletes to respect their ROOTS: Rules, Officials, Opponents, Teammates and Self. In Middle and Older Kids, we discuss ways you can show this respect and good sportsmanship.