Firearms are pervasive. Even in countries with strict gun control laws, it's possible to come across one. It's important to understand some elements of gun safety to keep people from coming to harm with these dangerous instruments.
Things Non-shooters Should Know
Guns Don't Shoot Themselves
Guns will almost never fire unless you pull the trigger1. If a person, especially a child, is not familiar with firearms, then they shouldn't touch them. If one is found where it shouldn't be, leave someone responsible to guard it, and send someone to call the police. Don't pick it up and take it to the police or school to turn it in. The police will come to you. Just don't touch.
All Guns are Loaded
Treat all firearms as if they're loaded, locked, cocked, and ready to fire. Numerous tragedies occur when people handle weapons as if they're not loaded. It's easy to shoot somebody, possibly yourself while just playing around2. Until a visual and physical inspection of the chamber has been carried out, the weapon should be considered to be loaded. As a matter of fact, even after you do that, it's still loaded.
If You Drop the Magazine, There's Still a Round in the Chamber
This is important to understand. When you place a magazine in an automatic weapon, you have to rack it, that is, pull the slide back and release it to make sure there's a round in the chamber3. When you rack the weapon, it takes a round from the magazine and puts it in the chamber.
The other side of this is that some people think that if you drop the magazine, the weapon isn't loaded. That's not the case at all. A few weapons are designed not to fire without a magazine in the weapon, but most will. Even a weapon with that feature might be defective, and could still fire.
Keep Your Finger Off the Trigger
Keeping a finger on the trigger of a firearm is inviting disaster. If there's not an immediate reason to pull it, keep it out of the trigger guard. If you slip, fall, or even flex your other hand, you might involuntarily pull the trigger without meaning to. Keep your finger along the trigger guard until you're ready to shoot.
Practice and Training
For people who do carry firearms, training is essential. First, everyone who carries a weapon or is even around weapons, should be very familiar with how they work. People who carry them must be prepared to employ them effectively. A person who can't shoot in a desperate situation can add to the danger that they are trying to prevent. Anyone who carries a weapon should take it to the range and fire it periodically.
Don't Point a Gun at Anything You're Not Willing to Destroy
Guns are meant to kill people and damage things. They do their job very well. You should always be aware of where your muzzle is pointing. If you are going to shoot at a target, make sure that you have it clearly identified.
Know What is Past Your Target
Keep in mind what is around and past your target. Many bullets will pass through a body. No one is perfect, and you may miss. Shooters should have a clear idea about what is past what they're shooting at to avoid accidentally shooting the wrong thing or person.
Alcohol or Drug Use
They impair your judgement and perception. They shouldn't be used along with a firearm.
Eye and Ear Protection
Guns are loud and they may throw off debris or hot gasses that could harm your eyes and ears. If you're shooting in a controlled environment, you should wear safety glasses and hearing protection. Also, remember that even when firing blank rounds, hot gasses will still be produced at the end of the barrel, so don't fire it too close to anyone.
Know the Law
To keep you out of jail and out of a civil suit, know what the law is about employing or possessing a weapon in your state or country4.
Maintain the Weapon
People who carry weapons should make sure that a firearm is in working order. Field strip it and clean it. Lubricate it occasionally. If the weapon fails during a shoot situation, you've substantially increased the danger to everyone involved.
Safe Gun Storage
Firearms should be kept in a safe location and in a safe condition. That usually means out of reach and unloaded with the ammunition stored separately. When they are being stored, make sure that they're protected from unauthorised access.
Many people keep them in gun safes or use gunlocks that prevent the weapon from being fired without removing the safety. One very important point about gunlocks, is that they shouldn't be used on loaded weapons. There might be an accidental discharge while you're manipulating the lock.
The first thing you should do when picking up a weapon, is clear it to make sure that it isn't loaded. If you don't know how to do this, leave it alone. You shouldn't be picking it up.
A Final Thought
Shooting can be a fun sport. Shooting might become an unpleasant necessity. Safety is paramount when dealing with weapons that can so easily kill, maim or injure. If you're not trained, don't touch them. If you are trained, keep it safe.