Hammer, first you want a very firm grip. Next you need to ensure that you do not relax your grip after you've pulled the trigger. Also be certain that you are gripping the weapon properly in the first place. When you grip the weapon, it's barrel should be in line with your forearm.
Second. Learn to lock both your wrist and elbow.
Third, apply a little isometric pressure with your support hand. Your gun hand is pushing forward, your support hand is pulling back. Not enough pressure either way to be uncomfortable, just enough to tighten everything up.
Here are three simple exercises you can perform while watching tv to build up requisite strength. Squeeze a tennis ball or other type grip strengthing device. When you think your fingers are going to fall off, go to the next exercise. For the wrists, attach a weight to a string. Attach the string to the middle of a 12 inch length of broom stick. Wind the string, lifting the weight, by turning the stick with both hands. When it becomes easy, attach more weight. For everything in the arm, fill an empty gallon milk jug with water. Hold it with your trigger-finger arm fully extended for as long as you can. Rest and repeat as many times as you can stand it.
