as in duels. press the right thumb stick down and hold it till it says draw. then hit draw key (L2 for ps3) aim gun at point to shoot and wait till white crosshair appears. then hit the fire button (R2 on ps3) if you nail the most white crosshairs you shoot first and win.
also aim for hand in none storyline duels it will disarm and only need 1 shoot to win the duel