In reality, all other rules stem from the simple assumption that the firearm is ready to shoot at all times. If you assume that the gun is loaded, and you are a reasonable individual, you should be fairly safe with it. Almost every unintentional discharge is followed by the words "I didn't think it was loaded," if the fool doesn't kill himself. If you know the gun has the capability of destroying whatever is on the other end, you should be reasonable enough to consider where that bullet might end up at any given time. The trigger rule is also frequently ignored, though. It always seems like such a convenient place to keep your finger and "that's where it's supposed to go," but many accidents could be avoided simply through good trigger discipline.