A huge pet peeve for coaches are players who play one sport, or do not cross-train the body to improve in their sport. There is a simple recipe to be great hockey player; be a skilled athlete. It is no secret that the best players on each team are typically good athletes. Being athletic is not always genetic. Athletes must practice and develop. All athletes had to work on it, a lot!
The cornerstones of athleticism are strength, power/explosiveness, agility, endurance, and body control. These can all be improved no matter where the starting point or what the level is. Young athletes need to take part in drills that require body weight strength movements, jumps and up-downs, direction-change, and body control. The practice of such drills will increase endurance, or the length of time an athlete can compete.
Advice: Play multiple sports! Every sport requires different muscle groups and body movements. The best athletes can play multiple sports well. Stay active! Go for hikes, runs, set up obstacle courses, do body weight workouts, play pickup games. Anything that requires the body to move and improve, the better!