You see, a good teammate shows up on time. For practices. For games. For anything the team does. Because a good teammate follows the team's rules, not his own.
But a good teammate does more than just show up. A good teammate plays hard and hustles, especially in practices, because he or she knows that players who play hard in practices will play hard in games.
A good teammate supports and encourages their teammates. And no way a good teammate would ever get in a fight with another player. A good teammate is throwing passes to teammates, not throwing punches at them.
Finally, a good teammate accepts the coach's decisions. Even the ones he does not like. Because a good teammate is always thinking about what is good for the team, not just himself.
So there you go. It isn't that tough. Just show up on time. Play hard. Get along with your teammates and your coaches. And you will be a good teammate.