We're talkingn pistols right?
I taught pistol shooting in the Army. I was amazed how poorly some shooters shot. At 15' they'd miss the entire target. Just terrible. I had been shooting pistols since I was 16 and was good at it.
Biggest single first error: Looking at the target and not at the sights. Placing the front sight on the target and now lining it up with the rear sight.
The secret to shooting a pistol is to stare hard at the sights. Line the top of the front sight with the top of the rear sight, make the two parallel lines on light on either side of the front sight the same size.
Hold the pistol deeply into the hand, the lower the center of gravity the better. Don't squeeze the gun too tight. Firm is tight enough. If shooting two handed place the non-firing hand over the firing hand and lay your thumb on top of the shooting thumb gently apply pressure. You can practice this at home with an empty pistol. Shoot with both eyes wide open. Take a deep breath and exhale, then another and let half of it out. Firm up your sight picture and ease the pressure on the trigger.
It is excellent practice to shoot one handed. Do it as often as you can and practice. Only dry fire a .22 with a snap cap in the chamber. Shooting one handed is excellent practice for shooting with two. You will find that you can hold the pistol with two as still as if you are shooting a rifle, if you practice one handed.
Shoot off hand and off eye one and two handed. You'll have to squeeze you strong eye closed to do this. This trains consentration and there are tactical applications for shooting with your weak hand/eye.
I practice by walking along a dirt road shooting at pebbles. I suggest using a Ruger Single Six or a Bearcat. I seldom plink in the woods with an auto. It's just easier and I think safer to shoot and reload a revolver. I shoot at pebbles the size of a nickel at about 20'. Pine cones at say 25 yds.
Shoot at long range. I usually shoot at long range using both hands. I've shot thousands of rounds through a little 2" Smith 36 at beer cans at 50 to 200 yards. Do not hold over. Put the front sight up in the "U" of the rear sight. At 150 yards with a Browning High Power I hold about half of the front sight high. Practice. You will be astounded how well you can hit at long range. It is a real confidence builder. They try it one handed and then off handed.
Sitting with your elbows resting on the inside of your knees using both hands you'll be able to shoot a very long ways. It'll take you two to three shots to walk your rounds to a target the size of a basket ball at 200 yards. At 500 I'll make a man put his head down.
I call it the "zin of pistol shooting". It's a head trip like a golf swing. Be metholdical and concentrate hard. When I was in my 20's I'd shoot a brick a day while walking through the woods. I did this Saturdays and Sundays most every weekend for a decade or so. Wear plugs and muffs. Even at that you'll still screw up your hearing. I'm bout half deaf. I'm still a good shot though and I still enjoy the dickens out of pistol shooting.
After practicing like this you will find it pretty easy to keep all your shots in the 10 ring at 25 paces. 15' is a piece of cake. At 25 yards with a accurized Smith revolver and wad cutters you'll shoot a group the size of the palm of your hand. I shot on the pistol team in the Army with the .45. Fun shooting. They issued us special guns; made a big difference.
I'm an old guy now and not as good as I once was. I shoot a Smith 25-3, a 45Long Colt. They come from the factory timed and with a very nice trigger. I reload lightish loads and enjoy the pistol.