There are three basic shooting stances that are taught to the majority of shooters. These three shooting stances are good for almost any kind of shooting, including both target shooting and also as part of defensive shooting training. These are also the shooting stances that are taught to professionals including police, federal agents, and military personnel.
You should learn at least one, if not all three, as each has benefits and drawbacks.
Step 1: The Weaver Stance
The Weaver stance is something like a "fighting stance" of a boxer or martial artist but optimized for shooting. To assume the Weaver stance, start with your feet shoulder-width apart and take a half-step backward with the same foot as your shooting hand while bending your knees. Extend your shooting arm straight out without locking the elbow. Lean forward until your center of gravity is just over the lead foot. While doing this, bring your shooting hand up to support the shooting hand, which should result in your support arm bending at the elbow.
Your eye should align with the sights once you've assumed the position.
The benefits of the Weaver are a "push-pull" tension on the firearm; your shooting hand naturally pushes the pistol forward while the support hand pulls backward.The Weaver is easy to move in while pivoting away from your dominant (shooting) side and can be employed with handguns and long guns alike. However, recoil is felt most in the wrists which some shooters find uncomfortable and cross-eye dominant shooters have difficulty as the Weaver favors the strong-side eye as this stance pulls the pistol to the strong side.
Step 2: Isosceles Stance
The Isosceles stance is so-named because an overhead view of a shooter in this stance would resemble an Isosceles triangle. To assume the Isosceles, place your feet shoulder-width apart and bend the knees. Bring both arms up until you hold the pistol directly in the center of your field of vision. Arms should be fully extended, with a slight bend in the elbow and the shoulders square to the target.
The Isosceles is easy to assume for many shooters and the most intuitive stance, as it's very easy to assume. It will seem the most natural, as it is. You can crouch as deeply as you like and many defensive shooting instructors recommend as deep an Isosceles stance as possible, as this minimizes the target presented to an opponent. It is also very easy to move in the Isosceles
However, the Isosceles is not the most adept at managing recoil, requiring shooters to maintain a very hard grip on the pistol. This leads some people to stagger the strong side foot to create the Modified Isosceles, which is a bit better at managing recoil.
Step 3: Modified Shooting Stance
The Modified stance, which is sometimes referred to as the Modified Weaver or the Chapman stance, combines the best features of both.
This stance assumes the position of the Weaver, with the dominant foot a half-step back and knees bent. The support arm is brought up to the shooting hand and bent for support, and the Chapman/Modified stance retains the push-pull dynamic of the Weaver. However, the shooting arm is extended to the point of the elbow locking. To acquire the sight picture, the shooter leans their head toward the shooting arm.
Unlike the Weaver, which forces the shooting arm away to the strong side, the Chapman/Modified allows cross-eye dominant shooters to acquire a sight picture by just leaning the head a little further in. In some instances, this results in a "cheek weld" to the shooting arm just like when shooting a rifle.
The advantages are that the Modified stance allows for cross-eye dominant as well as non-cross eye dominant shooters to easily acquire the sight picture. Since it retains the push-pull of the Weaver but aligns the arm so the body can absorb more than in the Weaver, it also manages recoil better as the shoulders and upper body bear the brunt rather than the wrists. However, it can be a little slower to assume but not by too wide a margin.
Step 4: Concealed Carry Training
A person should familiarize themselves with each stance, and learn which suits them best. You'll likely find one that works best for you, though a person will ideally be able to use any of them effectively.
If you are interested in learning how to train for concealed carry, we wrote a lengthy guide "The Complete Concealed Carry Training Guide". Take a look if you have time, it's a lengthy read bout 30 minutes.