You should first find out how convenient you can direct a Firearm before buying it. Hold the empty gun and close your eyes and point it in a safe direction, with the finger position next to the trigger (not exactly above it). Go to a fixed target. Open your eyes or the objects you see should be exactly where you want them to be. At a distance of 4.5 meters, your position should not be more than a few centimeters from the center of the target.
Try a variety of firearms whenever possible. Use a handgun that feels good in your hand when you shoot
Think carefully about whether you will be able to pull the trigger on other humans or not. Apparently pulling a firearm is a good idea to frighten a criminal, but often it just exacerbates the situation, and makes it worse, especially if you can not fire it.