1. ALWAYS keep the gun pointed in a safe direction.
2. ALWAYS keep your finger off the trigger until ready to shoot.
3. ALWAYS keep the gun unloaded until ready to use.
   

The Canadian Firearms Program uses the concept of The Four Firearm ACTS:

1. Assume every firearm is loaded.
2. Control the muzzle direction at all times.
3. Trigger finger off trigger and out of trigger guard.
4. See that the firearm is unloaded. PROVE it safe.

Trigger locks prevent motion of the trigger. However, a trigger lock does not guarantee that the firearm cannot be discharged. Some trigger locks are integrated into the design of the weapon, requiring no external parts besides the key. Generally, two pieces come together from either side behind the trigger and are locked in place, which can be unlocked with a key or combination. This physically prevents the trigger from being pulled to discharge the weapon. Other types of trigger locks do not go behind the trigger, but encompass the full area behind the trigger guard making the trigger inaccessible.
There is controversy surrounding manufacturing standards, usage, and legislation of trigger locks. While supporters of trigger locks argue that they will save children from dying in gun accidents, critics point to demonstrations that some models can be removed by children with very little force and common household tools. Many firearms can go off if the gun is dropped. It is important to make sure to look for firearms that fully disengage the hammer when the safety is put on. A former senior product manager at Master Lock, a trigger lock manufacturer, was quoted as saying “If you put a trigger lock on any loaded gun, you are making the gun more dangerous.” Critics also point out that a trigger lock will increase the time it takes a gun owner to respond to a self-defense emergency. In 2008, the U.S. Supreme Court overturned a Washington, D.C. law that required handguns to be locked or otherwise kept inoperative within the home, saying that this makes it impossible for citizens to use them for the core lawful purpose of self-defense.
Although there are no universal standards for the design or testing of trigger locks, some jurisdictions, such as the state of California, maintain a list of approved trigger lock devices.In Canada, a trigger lock is one of the methods prescribed by law to secure a firearm during transport or storage.

• Cable locks

Cable locks are a popular type of chamber lock that usually threads through the breech and ejection port of repeating-action firearms; they generally prevent full cycling of the action, especially preventing a return to "battery", with the breech fully closed. In many designs of pistol and rifle, they also prevent the proper insertion of a magazine.
California effected regulations in 2000 that forced gun locks to be approved by a firearm safety device laboratory via California Penal Code Section 12088. All gun locks under this code must receive extensive tests including saw, pick, pull, and many other tests in order to be approved for the state of California.
Open bolt indicator

Shooting ranges may require that firearms not in use have the bolt, slide or (in case of revolvers) cylinder locked open to expose the firing chamber as empty. In addition, an open bolt indicator, such as a yellow safety flag may be inserted in the barrel (needed if the firearm design lacks a mechanical hold-open device). This is particularly important when shooters go down range to set up, score or remove targets.

Children

Children who are generally considered too young to be allowed to handle firearms at all can be taught a different set of rules:

• Stop.
• Don't touch.
• Leave the area.
• Tell an adult.

The purpose of these rules is to prevent children from inadvertently handling firearms. These rules are part of the Eddie Eagle program developed by the NRA for preschoolers through 6th graders.
Whether programs like Eddie Eagle are effective has not been conclusively determined. Some studies published in peer-reviewed journals have shown that it is very difficult for young children to control their curiosity even when they have been taught not to touch firearms. Gun access is also a major risk factor for youth suicide. The American Academy of Pediatrics (AAP) advises that keeping a gun in the home, especially a handgun increases the risk of injury and death for children and youth in the home. If families do keep a gun in the home, the AAP advises keeping it unloaded and locked up, with the ammunition locked in a separate location, and the keys to the locked boxes hidden.
Polling shows that over half of parents who do not own a gun have never talked with their children age 5-17 about gun safety.The ASK Campaign (Asking Saves Kids) is based on the fact that many families with children have a gun, and almost half these guns are left unlocked or loaded. The ASK Campaign urges parents to ask their friends, neighbors and family members if they have a gun in the home before sending their children over to play.
Older youth (age may vary per program) may take part in a program for safe rifle handling, such as the ones promoted by these organizations:

• 4H Shooting Sports Programs
• Boy Scouts of America
• National Rifle Association
• Civilian Marksmanship Program