Grab the pull-up bar with your palms facing your torso and spaced at a width more narrow 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, pause briefly (squeezing your back and bicep muscles) before slowly lowering 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 for very high repetitions, try adding weight via a weight belt to make the motion more challenging.