Dirty light fixtures can emit up to 20% lesser light than clean ones, so regular cleaning and dusting go a long way toward brightening your living spaces.
For safety purposes, never attempt to clean or work on a lighting fixture with an active electrical current. The best bet is to unplug fixtures or turn off the circuit breaker prior to cleaning. Also, never allow liquid to touch wiring.
Wash coated metal surfaces with a clean soft cloth soaked in detergent and warm water; rinse thoroughly. Dry the surface with a clean soft white cloth.Do not use abrasive, acid, alcohol-based, or solvent-based cleaners; they may damage the finish.
In case the glass globe/shade can be removed; support the glass firmly with your hands while you remove the screws or clamps holding it in place. When you've safely removed the glass from the fixture, dump any dirt or dead bugs out into the trash and fill a bucket or your sink with warm, soapy water. Soak the glass in the water for a few minutes.
Also, do take a look at the light bulb(s) themselves and determine if they need any attention. If your bulbs have a dirty film on them, your room may be getting less light than it should be! Using a damp cloth, very gently wipe any residue from your bulbs and allow the bulbs several minutes to dry completely. Replace the bulbs into their fixtures.
After soaking the glass for a few minutes, use a sponge or cloth to wipe away any remaining grime, then dry it completely with a towel. Replace the glass with the screws or clamps.
If you can't remove the glass or would rather clean them in place, be sure to spray any water or cleaning solution onto a cleaning cloth first, not directly onto the fixture!