Turn off the water supply and flush to lower the water level
Wear gloves
Sprinkle baking soda around the ring
Pour white vinegar over the baking soda
Let it sit for 15 to 30 minutes
Scrub the ring with a toilet brush
Use a pumice stone on stubborn mineral rings, keeping it wet
Apply a toilet bowl cleaner made for hard water stains if needed
Let the cleaner sit according to the label directions
Scrub again until the ring is gone
Flush to rinse the bowl
Repeat if necessary