The first and most important rule for handling firearms is to always treat every gun like it is loaded. When I was in high school a friend of mine was shot and killed because another individual was cleaning a handgun and assumed it was not loaded. If you treat every gun like it is loaded, it eliminates the potential for accidents such as this. Always be mindful of where the gun is pointed. Never point a gun at anything you do not intend to kill. The best direction to point a gun is straight down towards the ground. The second best direction is straight up in the air. If there is an accidental discharge, this helps to prevent the round injuring other people.
Always keep your safety on until you are ready to fire. Most rifles, shotguns, and handguns have a safety switch somewhere. This locks the action so that the gun cannot fire even if the trigger is pulled. Know where that safety is located and do not switch it off until your sights are lined up and you are ready to fire. After you have fired, immediately switch your safety back on until you are ready to fire again.
However, never assume that your safety will prevent the gun from firing. They are not 100% effective. The only truly safe gun is an unloaded gun. Also, do not put your finger on the trigger until you are ready to fire. Get in the habit of resting your finger outside of the trigger guard and only move it when your target is in sight.
Never look up the barrel of your gun and never ask anybody else to do so. There are times when you need to ensure that the barrel of your gun is clear. If your gun has been dropped in the dirt, in the mud, or in snow then a clear barrel is essential. However, looking up the barrel of the gun with it pointed at yourself is very dangerous. Most guns will allow you to look down the barrel from the rear, or at a minimum will allow you to do so after being partially disassembled. This is the safe and proper way to check your barrel.
Do not jack a round into the chamber until absolutely needed. Most firearms will allow you to load the gun without actually putting a round in the chamber. When I go hunting I like to load the gun before leaving the house, but I do not chamber a round until I am in position and ready to actually start hunting. This is just another safeguard to prevent an accidental discharge.
As soon as you are done shooting, empty your weapon. When finished, I always remove the clip or jack all remaining rounds out of the action. I also jack the chamber empty several times to ensure that the gun is completely clear. I then immediately store all rounds back in their case so there are no loose rounds rolling around in the vehicle or in my pocket.
Always be conscious of the range of your weapon. When firing bird shot out of my shotgun, I know the range is less than 100 yards. When I fire at birds, I only have to be cautious not to aim at any other hunters or dogs within that range. However, any of my rifles have the potential to travel much farther. Any time I fire a rifle I always find a downward shooting angle so the round ends up in the dirt. Also, never assume that your target will stop the bullet. It is not uncommon for a round to enter the target, exit the opposite side, and keep travelling for a long distance. Be mindful of what or whom is behind your target.
When hunting in a group, keep everybody in a straight line. The primary time this may happen would be bird hunting. If all hunters walk in a straight line then you just have to ensure that everybody shoots strictly at birds in front of them. This will prevent everybody from accidentally shooting the person next to them. If one person is out a few yards ahead of the line, it is easy to allow your aim to follow a bird right into their path.
Never walk down range until everybody is done shooting, safeties on, and are aware that you are headed down range. When you spend your afternoon target practicing at your local range, there will be several points where you need to walk down range to check or replace your target. However, this can be a very dangerous walk if you are not careful. Make all shooters aware that you need to head down. Ensure they have their safeties on and that they have set down their weapons. Then communicate a second time that you are walking down range before you head that way.
Keep your gun clean. To properly take care of your weapons, they need to be cleaned on a regular basis. Ideally you should partially disassemble them and clean with gun oil each time you use them. This will prevent rust and keep them in pristine condition, but it is not just about keeping them pretty. Guns that have not been cleaned are more likely to have a mechanical failure. In some cases this can be dangerous for the shooter. Take the time to make sure your firearms are in good working order.
One of the most important aspects of gun safety is storage of your firearm and ammunition. All firearms should be stored in some sort of a locked enclosure. This could be a gun safe or a gun case, but the lock is vital. You also need to store your ammunition in a different location. This makes it more difficult for children to end up with a loaded gun, and also gives you an added layer of protection if a burglar breaks into your home.
Never fire questionable rounds. If you are anything like me, you will occasionally run across random bullets or shotgun shells as you dig through your hunting gear. If you do not know what kind of round it is, you are better off not to fire it. Also, if it looks like it may have been damaged you will want to get rid of that round. Only fire rounds that are designed for your gun. It can be dangerous to fire improper rounds, even if they fit in the chamber.
Never intentionally fire your gun straight up. Do not forget that bullets that are fired upwards will have to eventually come down. In many cases they will descend at speeds fast enough to kill or injure a person. Guns are not for celebrating, so only pull the trigger if you have a target in your sights. Also never fire at anything metal. Ricochet shots can be very dangerous. If you fire at something metal, the bullet will likely bounce off. You definitely do not want it headed back in your direction.
Be cautious with how you carry your gun. Many people like to tuck a handgun into their pants in the front or back. It is very easy for this firearm to accidentally discharge, and it could possible shoot you in the leg. Always use a proper holster that is designed for holding firearms. Also, never climb a tree stand with your gun in hand or slung over your shoulder. It would be easy to drop the gun or snag the trigger on something. Bring cordage with you and attach it to your gun. Once you are in your stand, use the cordage to pull the gun up to you.
Always wear eye and ear protection if possible. The sound emitted from a gun being fired is loud enough to damage your eardrums. Ear plugs are always a good idea, especially if you shoot frequently. Loud noises have a cumulative effect on your ears. Safety glasses are also smart to help protect your eyes from shrapnel or smoke. Many ranges require this safety gear to be utilized.
Never fire a weapon if you have been drinking alcohol or if you are on prescription medication. Firing a gun is very much like driving a car. If done safely it can be very productive, but you never want to take your chances if you are not 100%. Firing a gun while intoxicated significantly increases your chances of injuring yourself or others. It is also against the law in many states.
If you follow these rules, shooting and hunting can be a wonderful hobby. If you have not taken a hunter safety course, I highly suggest you do so. The course will go into much more depth and will make sure you are ready before you start hunting. In some states this is required before you can purchase a hunting license. Once you know how to be safe with firearms, you are ready to enjoy them to their full potential.