Safety Rule: Service panel.
When you decide to undertake electrical projects, big or small, always turn off the power to the area or device you are working on. Check to make sure electricity is off by using a circuit tester to test voltage.
Safety Rule: Rubber
Wear rubber-soled shoes when working on electrical projects, especially if you are working on electrical projects while standing on a damp floor. Rubber is a poor conductor of electricity, thus preventing you from being shocked.
Safety Rule: UL Approved
Make sure all your electrical parts or devices are UL-approved. “UL” stands for the Underwriters Laboratories; they are an international organization for product safety testing and certification.
Safety Rule: Extension Cords
It is important to not misuse extension cords. Extension cords are for temporary use only. It is important to use the right type of extension cord for your particular needs.
Safety Rule: Label Breakers
Create a panel directory and stick it on the inside of the door of your main service panel. You will need to update the list as necessary. This is so that you won’t waste time searching for the correct circuit, especially in an electrical emergency where you may need to turn the power off in a particular area of your house.
NB. You should never try to alter the prongs of a plug to fit a receptacle. If it's possible, you should install a new grounded receptacle.
For more on electrical safety read "Extension Cord Safety".