⇔ Never attempt to fix machinery that is energized. By using a tester, always verify that it is de-energized first. Before starting with your job, check all the cables, the outer metallic covering of the panel board and any other hanging wires with an electrical tester.
⇔ Then always turn the mains off while you are working on some receptacle at your house. It's also a smart idea to place a sign on the service panel so that no one inadvertently switches the key light on.
⇔ Especially, when dealing with power, stop water at all times. Never approach or attempt with wet hands to patch any electrical appliances or circuits. It improves the electric current's conductivity.