If you have heard it once, you have head it a thousand times: squeeze the trigger, don't jerk it-nobody likes a jerk. The reason for this is simple. If you slap that trigger, you are going to pull your muzzle off target. At close range, you won't notice it, but at distances 7 yards and further, the slap of a trigger can lead to throwing off your shot by several inches.
Further back and you won't even hit the target at all.
One sure way to fix this is to train your brain to have a slow and steady trigger squeeze. A trick that has worked for generations of shooters is the old quarter trick.
What's that, you ask? Keep reading.
With this simply place a coin, the larger the better (quarters and similar tend to work best), on the top of the slide of an *unloaded semi-auto near the front sight, or the top strap of a similarly empty revolver and dry fire it. If you have a good, smooth trigger squeeze, the coin won't fall off. If not, then the result will be obvious.
*(check it twice, drop the mag, work the slide three times and point in safe direction at all times)
Keep working on this slowly until you can keep the coin on there for one or two clicks of the hammer. Most modern centerfire handguns can be dry fired without causing any damage to the hammer or firing pin, however, snap caps (they are cheap and never wear out) can be used to make sure. Once you can keep that coin up there and on target through a solid 100 trigger squeezes, you should be in business with a nice, smooth pull.
Note, each model firearm is different so you need to work on this to train your brain where the trigger breaks at, and therefore helping you aim point stay true. This also works on rifles by putting the coin or washer on the muzzle behind the front sight.
Another, more expensive alternative is a SIRT training gun. These run about $200~ (shop around, the interwebs are your friends here) but offer real time, safe firearms training for not only trigger squeeze but also sight alignment and grip.
Destinee giving you the 411 on the SIRT. It has some pluses and minuses.
You will sometimes see a lot of talk about breath control and breathing sequences. While some maintain that you should regulate your breathing and only take a shot between breaths, this can sometimes be unrealistic, especially in a self-defense situation. In a long-range target environment with unlimited time, go for it, however if training for more real-life issues, simply breathe normally. Too often shooters who try to control breathing simply hold their breath at weird times or worse, force themselves into hyperventilating. Stranger things have happened.
Now another issue with trigger control is just where you actually touch the trigger with your finger.
A good way to locate your index finger's "sweet spot" is to pinch something with your index finger and thumb. That part where the two come together and apply pressure? Odds are that is the exact part of your finger that you want to use on the trigger pad. Typically, this will be midway between the tip, and the joint between the first and second digit.
As this image shows, proper trigger squeeze from the correct part of the index finger, midway between the tip and the end of the first digit, will go a long way towards getting you center mass hits. Too much tip and you will see shots pushed to the offhand side of the target-or off it entirely. Too much finger or a trigger slap will have your rounds impact to the strong hand side of the target edge.
So what are you waiting for? Grab a quarter and get to work.