Article: The best way to do this is by turning off the electricity supplied to the circuit on which you will be working at the junction box (also called a fuse box) for your home. Switch the breaker of your fuse-box so the fuse for the circuit supplying electricity to your fixture reads "Off." It's always a good idea to double-check the flow of electricity by checking the light itself before moving forward with this project. Flick the light on, and if the circuit has been disabled, the light should stay off. If the light you are wiring is in the ceiling, you should clean any cobwebs and dust before attempting to install your new fixture. The same is true for lights or switches in walls; a clean work area will improve your ease of installation. If you are using a ladder to reach your light fixture, or are in a less than ideal position, be sure the ground is also clear of debris or anything else that might affect your balance or safety. There is usually, but not always, a decorative globe, shield, or some kind of external feature covering your existing light fixture. This could also be something more involved, like ceiling fan blades. There will be a mounting bracket holding your old fixture in place. You will need to unscrew this from mounting bracket, usually with Phillips-head screwdriver, and then pull it from the bracket. Be sure you support the old fixture with your hand as you unscrew it from the mount. If you do not support the fixture, it could fall to the floor once you loosen the screws holding it in. Allow the unscrewed fixture you are supporting with your hand to descend a few inches below its mount. You will likely see three wires attached to your fixture: a hot wire, grounding wire, and neutral wire. You will need to use your free hand to uncouple these wires, twisting the wiring cap to free the wires from each other.  Hot wires are those that run electricity to your fixtures and grounding wires are intended to offer surge electricity a neutral point, like the earth, into which it can dissipate.  In some cases, a grounding wire might be attached to the mounting bracket itself, rather than a house wire. This is fairly common in new light fixtures. You should see plastic caps, called wiring caps (also called a wire nut), with two wires running into each cap. One wire will come from the light, the other from the main electrical circuit of your house. Disengage the wires by twisting the wiring cap until it comes free. Once you have released the light from its wiring, you can set the existing light fixture aside.

What is a summary?
Cut power to your circuit. Clean the old fixture and installation area. Remove the old fixture covering. Unmount the fixture. Lower the fixture. Disengage your light from its wires.