Coaches must EMPHASIZE reducing turnovers. As a team we discuss turnovers and accountability. The team is not accountable to me but to each other and players agree that repeated turnovers mandate substitution. "The ball is gold." "Value the ball." "Take care of the ball." Players need correction and must give feedback after the correction.
Turnovers often cost you twice, preventing a scoring opportunity AND providing a high quality (e.g. transition, layup) scoring chance for your opponent. Turnovers are in the 'big four' analytics of Dean Oliver that decide outcome - shooting percentage differential, turnovers, rebounds, and free throws taken.
Preventing turnovers starts when you walk into the building. Coaches and players should identify boundary asymmetries (illusions) that lead to players catching the ball out of bounds. In one game, I pointed out to players how often players will misidentify the boundary in this gym. Sometimes the officials are even confused about boundaries and we review those before the game. Our opponents caught the ball out of bounds FIVE times. We still did once. Lighting conditions can make catching or shooting difficult in some gymnasiums. Some gyms have 'dead spots' that you can identify before the contest. Not knowing where the shot clock is can cause critical errors.
In addition to the "obvious" turnovers like bad passes, traveling, and violations, many subtle errors contribute to lost possessions or half lost (held balls). Doc Rivers called hideously bad shots "shot turnovers." Failure to block out is a "rebounding turnover." Passing to poor receivers in transition or poor shooters in key situations equates to a turnover.
Charging causes both loss of possession and foul trouble. Offensive fouls like illegal screens have similar impact. Fouling an opponent taking a low quality shot can be even worse than a turnover, resulting in two or three free throws instead of a change of possession. "Standing around" instead of moving without the ball can cause violations. Cut, screen, or sit.
Failure to complete a cut can cause a good pass to become a poor one. Alligator arms (bailing on a rebound or catch) or failure to come to the ball ("shorten the pass") contribute to "bad passes." Failing to protect the ball or pivot intelligently allows held balls and half a turnover.
Failing to understand situational basketball causes mental mistake turnovers. Taking a timeout you don't have is a technical foul. Holding the ball end-of-shot clock or end-of-quarter denies a scoring opportunity, and shooting early in a potential final possess affords the opponent another possession. Turnover.
Don Meyer had a saying, "what is unacceptable in defeat is unacceptable in victory." When we accept poor quality play we take ownership. Back in the day, our coach would roll tape over and over imprinting the mistake on formative minds. It wasn't humiliating. It was frustrating but it changed behavior.
Crushing the turnover bug is always a worthwhile discussion in a game where 'every possession matters.'