You and your teammates who are guarding players without the ball, should be trying to create a situation in which the player with the ball has no one to pass to.
Consequently, each moment during play, when you are guarding an opponent without the ball, your task is to 'deny' your opponent from receiving a pass, by blocking the passing lane and stopping him/her from executing a ball cut. A ball cut occurs when your opponent cuts between you and the ball.
Dropping to the Ball
To play deny defense, you must learn to "drop to the ball." The maneuver requires that you continuously adjust your location on the court in relation to the player you are guarding and the player with the ball. The greater the distance between these two players, the greater is your drop to the ball. The drop is always toward the ball and the middle of the court.
There are factors other than distance between the player with the ball and your check, which will determine the degree of your drop, such as your athletic ability and skill of your check, as well as the player with the ball. For example, particularly in full-court play, when the player with the ball is guarded by a taller player, the player with the ball will have considerable difficulty throwing long passes over the taller defender. Knowing this, you and your teammates can execute a considerable drop.