Some people like to use the "slingshot" (?) technique, where you pinch the back end of the slide between your thumb and the knuckle of your forefinger. But, this requires a fair amount of strength in your hand.
Many advise it is preferable to grasp the slide between the tips of your fingers and the heel of the hand ("power grip"). Most people will find they have much greater strength with this kind of grip. Then, you can either pull back with your grasping hand, or push forward with the hand on the grip of the weapon, or a combination of both.
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