Cleaning the Inside
Remove any dust webs from around the skylight using a broom. Place a dropcloth beneath the skylight and keep it in place until both the interior and exterior are cleaned.
Attach a rag to the end of the broom using duct tape.
Apply a generous amount of glass cleaner to the rag. Wipe the skylight with the rag.
Use a long-handled squeegee to wipe the skylight if it is a flat panel.
Dry the skylight using a clean rag. Repeat this cleaning procedure every six months to keep the skylight clean.
Cleaning the Outside
Add 1/4 cup of liquid detergent to a bucket and take it up to the outer skylight surface using a sturdy ladder. Add water to the soap with a garden hose.
Hose down the skylight with clear water. Spray on a small amount of citrus based cleaner if there is bird excrement or tree sap present.
Clean the skylight by scrubbing the surface with the soapy water and sponge. Rinse with the garden hose and allow the surface to air dry.
Apply a layer of automotive wax to the skylight and buff with a clean rag. This will protect the surface from scratches and weathering, according to HowtoCleanAnythingcom.