How can coaches improve team performance?

First they need to know their players ability and their talent. They should know their players, so the players feel comfortable. Showing support through each and every player and helping on one another weakness. A lot of practice and helping the players and doing it over again until they have what you want them to do. Have them watch videos. Remember to have a positive mind and that it's not gonna work on the first try. 

Coaches plan, conduct, and evaluate the team on a regular basis. They are the leaders of the team, so they help motivate the players. They are able to communicate with the athletes and determine the best learning styles for each player. Coaches call the plays and the strategies. Without quality coaching, a team's strategy can diminish and lead to a team's demise.