Move away the furniture underneath the stain. Drape plastic sheeting over anything you are unable to move. Lay plastic on the floor directly underneath the stain.
Put on eye protection and rubber gloves to protect yourself. Position a ladder underneath the stain, and climb it to a height where you can reach the ceiling without stretching.
Wet a sponge with bleach or a household cleaner that contains bleach. Dab the ceiling stain with the sponge until the stain is gone. Allow the ceiling to completely dry.
Tape off the stained area with masking tape. Cover moldings and any ceiling areas between panels with the tape.
Spray a coat of "stain killer" primer/sealer on the stain. Follow the manufacturer's instructions for the amount of time to allow it to dry.
Paint over the stain using a paint brush or roller if the color of the primer/sealer does not match the ceiling color.
Remove the masking tape and plastic. Place the furniture back into position.