[m21sniper]

If AT ALL possible, start with a .22 rimfire. Barring that, the smaller the caliber, the better(but avoid a compact or pocket type of weapon, as their reduced weight and grip can make even light calibers difficult to control properly at first)

First, and most important, MIND YOUR MUZZLE AT ALL TIMES. NEVER, EVER, EVER point your muzzle anywhere but DOWN RANGE.

The keys to good shooting are concentration, breathing, and trigger control.

Firstly, AFTER you are sure the range is clear, block all external distractions from your mind. Nothing exists but you, the firearm, and your target. You want to be in a big time Zen state. Start at a target at close range. For a rifle 25m is plenty, for a pistol, 7m is plenty.

When aligning the sights on the target, focus on your front sight so that it is sharply focused. It's ok for the rear sights to be a little 'fuzzy', as you can't focus on both at the same time. Aim for the dead center of the target. The rounds may not go there, but what you want to do is make a nice tight grouping, where they hit is secondary to the desire to have them all as close to one another as possible.

When it comes to shooting, make sure to have a proper grip on the weapon. Precise instructions can be found on many websites as to the proper technique for holding a rifle or pistol.

Take a deep breath, then exhale some until you feel comfortable. Never fire while breathing, as this causes vertical stringing. (A vertical dispersion in your shot group). Then slowly squeeze the trigger until the weapon fires. Deliberately.

The weapon should surprise you when it goes off. If you expect the moment of recoil you will naturally flinch, so you want to surprise yourself as to the exact moment of firing so that when you flinch, the projectile is already long gone. This is where the .22 excels, as it has minimal recoil and muzzle blast, so your natural flinch will be greatly minimized as opposed to firing, say, a .357 magnum. If flinching is affecting your aim you will see horizontal stringing. Jerking the trigger can also cause horizontal stringing, but if you follow my advice and squeeze off slow, deliberate shots, you won't have any problems with jerking either.

If you see diagonal stringing, your aim is being affected by both breathing and/or flinching/jerking.

Once your trigger control is down (could take anywhere from a few hours to a few months depending on your natural talent and amount of practice), and you don't have any flinch issues, focus on firing between heartbeats. The beating of your heart actually affects your aim. At long range firing during a heartbeat can cause you to miss your target entirely by several feet. Don't worry about this in the beginning, as trying to time your shots precisely makes it difficult to squeeze the trigger slowly enough to surprise yourself when the firearm goes off.

Good luck.