Closing out on a shooter without fouling him
Defence
The defensive sprint and stop that happens dozens of times a game, broken into its parts.
A closeout is what a defender does when the ball is passed to the man he is guarding and he is several metres away. He has to cover the ground before the shot goes up and arrive under control, and those two demands pull against each other.
Sprint the first two thirds of the distance at full speed with long strides. There is no point being cautious while the ball is still in the air. Then, roughly two strides from the shooter, break the sprint into short, quick, choppy steps with the feet close to the floor. The chopping is what lets you stop without your weight continuing forward, and it takes practice because it feels slower than it is.
Arrive with one hand high, the hand on the side the ball is on, and the other hand low and out to your side. The high hand is there to obstruct the sight line to the basket, which affects a shooter more than a hand near the ball does. The low hand protects against the drive. Do not swipe at the ball on a closeout: the shooter is already raising it, and a hand coming down onto his arm is a shooting foul and three free throws if he is behind the arc.
Keep your feet on the floor. A shooter who sees a defender in the air will put the ball down or lean into him, and both produce free throws. If he pump fakes and you have chopped your feet properly, you will be balanced enough to stay down, and then you are defending a shooter who has already used his fake.
The angle of the closeout is a team decision rather than an individual one. You do not run straight at the shooter. You approach slightly off to one side, so that if he drives he drives toward where the rest of your defence is standing, usually toward the middle of the floor where the centre is waiting, or toward the baseline if your team prefers to trap him there. Running straight at him gives him both directions and forces your teammates to guess.
The sign of a good closeout is boring. The shooter does not shoot, he puts the ball on the floor, he goes the direction you wanted, and a second defender meets him. Nothing happens, the possession continues, and the shot clock loses four seconds. That is the outcome you are aiming for, and it happens perhaps fifty times in a game without anybody remarking on it.