The Four Basic Laws of Firearm Safety

Law 1
Always treat a firearm as if it were loaded.
By doing this you greatly reduce your chances of a negligent firing.

Law 2
Never aim a firearm, loaded or unloaded, at anything you are not willing to destroy.
Like Law 1, this will greatly reduce your chances of making a very serious and costly mistake.

Law 3
Never put your finger on the trigger or in the trigger guard until you are aiming at your intended target and are ready to fire.
Firearm trigger pull can range from very heavy 10 pounds or more to very light 2 pounds or less (hair trigger). Firearms will only fire when the trigger is pulled, the firearm is dropped and lands just right or there is a malfunction. Since it is designed to fire when the trigger is pulled, keep your finger off of the trigger until you ready to fire. The trigger finger should rest on the frame, slide or cylinder above the trigger and on the side of the firearm until you are ready to fire.

Law 4
Never handle a firearm that you are unfamiliar with unless you are being trained how to use the firearm by a responsible adult who is familiar with it.
Like Laws 1 and 2, this will greatly reduce your chances of a negligent firing.