Set the pulley height closest to the ground, pin a suitable weight and position yourself adjacent to the stack.
Take hold of the cable handle with the hand that is closest to the stack, palms facing upward. You should be facing in towards the stack so that the cable handle moves up and toward your body when you curl. Your arm is extended and at the side of your body, your core is tight and your feet are flat on the floor at shoulder-width. This is the starting position.
Commence the movement by curling the cable handle up from the elbow joint and squeezing your biceps. The elbows should work like a hinge with the forearm being the only moving part. Exhale through the movement. Do not use momentum to jerk the weight up.
When your biceps are at maximum contraction, squeeze for a second and then reverse the movement by extending the arms to the starting position, inhaling as you do.