Grab the pull-up bar with your palms facing forward at a prescribed width. A wide grip entails that your hands are spaced out wider than your shoulder width. A medium grip entails that your hands are spaced out at a distance equal to shoulder width. And a narrow grip entails that your hands are spaced out at a distance less than shoulder width. With your arms extended in front of you as you hold the bar, bring your torso back at about 30 degrees and create a curvature in your lower back by sticking out your chest. Pull your torso upwards until the bar touches (or almost touches) your upper chest. Imagine that you are drawing the upper arms down and back in order to properly engage your latissimus dorsi (the muscles that will give you that v-taper). Focus on keeping your upper torso stationary and ensuring that the forearms are doing no work other than holding onto the bar. Once you have lifted your entire body up by the bar, slowly lower your torso back to the starting position until your arms are fully extended once again. Repeat for the prescribed number of repetitions.
Once you can perform this exercise successfully at very high repetitions, try adding weight via a weight belt to make the motion more challenging.