Now that you've repaired the leak that caused it, how do rid your ceiling of that lingering brown water stain? Head to your local home supply or hardware store and pick up a can of pigmented stain blocker to brush on before you apply that new coat of paint. It's the secret to making ceiling stains--and odors--disappear.
Make sure the leak is fixed before removing a ceiling stain. Lay a drop cloth or a plastic sheet below the stained area of the ceiling to protect your carpeting or floor from drips. Standing on a stepladder, wipe the stained ceiling surface clean with a damp rag.
Apply a pigmented stain blocker such as Kilz or Bullseye on the stained area using a paint roller (for center stains) or a paintbrush (for corner stains). Paint 6 to 12 inches (15 to 30 cm) beyond the stain's edges.
Let the ceiling dry for 1 to 24 hours (follow the manufacturer's directions).
Apply a coat of ceiling paint. Let dry. Repeat if necessary.
For details on getting rid of mildew, see <a href="http://www.ehow.co.uk/how_113168_remove-mildew-walls.html" target="_top">How to Remove Mildew From Walls and Ceilings</a>.