A proper grip on a handgun requires both hands on the gun and a firm hold. There are slight variances between the grip on a semiautomatic handgun and on a revolver.
For a semiautomatic handgun, the dominant hand is placed on the handle with the thumb high and curbed down, and the nondominant hand is placed over the other one, facing forward with the thumb going forward along the slide. To hold a revolver properly, place it in the dominant hand all the way in the web of the hand. The trigger finger is placed along the frame of the gun. For a single-action revolver, the thumb is placed on the inside of the frame near the top so that it can reposition the hammer. For a double-action revolver, the thumb is placed on the handle for a better grip.