John Snow, the Shooting Editor at Outdoor Life magazine, explains the foundation of a solid, two-handed pistol grip.
The first step is to situate the stock of the pistol in the line between one’s thumb and palm. (Doing this gets the barrel of the gun straight in line with one’s forearm, and it allows for extra padding from the thumb). The trigger finger is indexed outside of the trigger, in line with the gun frame; the other three fingers of the shooter’s gun hand remain firmly on the pistol grip. The shooter’s support hand (ie, non-shooting hand) is then brought to the pistol. The index finger is placed under the trigger finger on the other hand. The gun is then driven forward with both hands–as the shooter does this, 70 percent of his grip strength should come from the support hand; 30 percent of his grip strength should come from his gun-hand.