The more I practice, train and teach the use of firearms the more I realize just how important the trigger press is to shooting accurately. Regardless of what you're shooting you always have to apply the fundamentals. But of all of the fundamentals – in my opinion – the trigger press is the most important.
This is mandatory in the beginning, learning how to smoothly press the trigger without tensing up muscles in anticipation of the recoil before, during and after the shot. The sights are always going to be moving; all the other components will never be perfect. As long as you press the trigger smoothly, letting the firearm "release" the shot, you'll get good hits.
In the beginning it's also important to take time to obtain the proper placement of the finger on the trigger. Position the finger so the trigger is centered in the pad of the first segment or "distal phalanges." This allows you to "feel" the trigger as you press and reset it, and helps ensure you're pressing straight to the rear without pushing or pulling the trigger and moving the muzzle. With consistent practice this placement becomes habit.
As you progress you learn what speed you can press the trigger in order to get good hits. With a close, large target you can press fairly quickly and get the hits. As the distance increases and/or the size of the target decreases you learn that a slower press is required to make the shot. Regardless of the speed of the press it always has to be a smooth press.
There are other trigger techniques used, and one can produce acceptable results with them, but these are more for specific applications. For example skeet and bird shooters will "slap" the trigger to release the shot. Some competitive shooters will "tap" the trigger. But to shoot as accurately as possible you're going to want to press that trigger.
I don't know how many thousands of rounds I've fired in my life so far. But still when I'm trying to shoot accurately – regardless of the type firearm, caliber or distance - I will say "pressssssssss" out loud, hissing like a snake while pressing the trigger. Verbally saying it out loud, extending out the last part of the "pressssssss" always produces good hits.
Also, keep in mind that as things get more complicated, such as when moving and shooting, the trigger press becomes even more important. For example when moving there's a greater tendency to go "now" on the trigger in an attempt to fire the shot as the sights move across the target. This leads to the dreaded anticipation, and is going to negatively affect your accuracy.
For defensive use it's important that you get accurate hits. Good hits stop the threat quicker. Accuracy ensures the safety of those in the environment; remember you're responsible for where each and every bullet ends up. The only way to produce this type accuracy under stress is to drill it on the range, under a variety of conditions. Then, when facing a violent attack and lives depend on you, "pressssssss" that trigger, and repeat as necessary.
Tiger McKee is director of Shootrite Firearms Academy, located in northern Alabama. He is the author of "The Book of Two Guns" - http://shootrite.org/book/book.html writes for several firearms/tactical publications, and is featured on GunTalk's DVD, "Fighting With The 1911 - http://shootrite.org/dvd/dvd.html McKee's new book, AR Skills and Drills, is available for pre-order: https://www.amazon.com/AR-15-Skills-Drills-Learn-Your/dp/144024720X/ref=sr_1_2?ie=UTF8&qid=1484771081&sr=8-2&keywords=tiger+mckee