Crush that Grip!
The Crush grip for most modern pistols has proven to be both the best for controlling recoil and most reliable grip for many different-sized shooters.
Crush grip means you are essentially squeezing the gun between your hands. This is also called the Cascading Thumbs grip because in its final state, the thumbs are cascaded over eachother, with the Support thumb slightly in front of and below the Primary thumb.
PRIMARY HAND
Forming the crush grip is very uncomplicated. First, you need to ensure your Primary or shooting hand is squarely behind the tang of the grip and as high possible without interfering with the slide.
You should respect the placement of your thumb on the side of the pistol. Too far forward, and your trigger finger will be too short to function properly, too far back and you will struggle getting your finger into the trigger frame.
If your grip fits your hand well, you should be able to reach the magazine eject button with your thumb. The middle knuckle on your trigger finger, while resting on the trigger guard, should also be nearly even with the trigger.
Of course all of this depends on your situation and gun preference, but don’t give-up your ability to manage your pistol effectively. you must have a gun that fits your hand properly. If the slide release is not accessible from your primary thumb, or the spring is too heavy, you have the wrong gun. If the grip is too narrow and does not fill your hand, leaving room on the side of the grip for your support hand, get another gun that works.
SUPPORT HAND
As you start to form your grip with the support hand, you will first need to understand how the support hand is canted or tilted down in order to ensure it is properly pivoted into your grip.
Take your open support hand and pivot it so the thumb is pointed directly out. Next see how far you can pivot-down your palm keeping your thumb pointed straight-out. At some point, it locks at the wrist and you cannot pivot any further. This is the ideal angle at which to grip your pistol.
It is critical that your pistol grip also provide enough room for the palm of your support hand to rest against the grip as well. Grip too small, and your primary hand will wrap too far around the grip leaving little room for the support hand.
Take your support hand and wrap it around your primary hand. The palm should start with good contact on the gun grip itself, fingers wrapped around the Primary fingers, beneath the trigger frame, and the thumb sits ahead and below the Primary thumb.
Now comes the crush part of the grip. Using your finger tips from both hands, press them against the gun and your primary hand. When you engage the finger tips you are actually engaging all of the grip muscles in your hand. Simply squeezing the grip without this attention and your crush will not be optimal.
STRENGTH
There are a lot of coaches out there with different views on the amount of strength you should apply to your grip. Most of them are usually directing you to grip stronger on your support hand. But I would argue there is only one way to grip with both hands: as hard as you can. But pay attention to your trigger finger. You can impact it’s fine motor ability if you apply grip also to the trigger finger. It needs to be independent.
Recoil from most pistols cannot be fully mitigated unless you are shooting small caliber ammo. The force that is transferred into a pistol from a 9mm or .45 is too great. And what's worse, if you apply only partial strength into your grip, you are controlling even less of the recoil than you could otherwise with a full strength, maximum grip.
Besides managing recoil, a loose grip leaves room for trigger problems. Take your left thumb and lightly grasp it like a pistol grip in your right hand. Then flex your index finger like you are pulling a trigger. Your grip fingers move, don't they? Now grip your thumb as hard as you can and try it again. Your grip fingers shouldn’t flex. That movement is what causes most shooters to hit their targets low and left (for right-handed shooters anyway).