Before you attempt to remove a ceiling stain, identify and repair the cause. Stains caused by roof leaks or build up of condensation will reappear until the problem is corrected.
Lighter stains can sometimes be removed with undiluted bleach, be sure to protect carpet, drapes, furniture and yourself before trying this remedy. Wear rubber gloves and protective eye wear (extremely important if you are working on an overhead problem area). Use a rag or sponge and dab the area with bleach until the stain has disappeared.
Very small, light stains can often be covered up with white shoe polish or chalk. For small nicks and dents in a textured celing, apply white caulk and contour to match the texture. Larger textured areas will require a ceiling patch product such as Homax Popcorn Ceiling Patch.
Severely discolored areas will require sealing and painting. Ceilings with smoke damage will also require sealing. Seal with a stain blocker such as Kilz (may take 2 coats), before reapplying paint or texture.