Cover the soleplate of a warm iron with a clean, thick towel.
Place the towel-covered iron onto the baseboard water stain and hold it there for approximately 5 seconds.
Remove the iron. The heat from the iron is likely to draw the moisture from the baseboard, which will remove the stain.
Polish the baseboard with furniture polish to restore its luster.
Make your own water-stain-removal polish. There are several options for this type of polish. Mix 1 tablespoon of baking soda with 1 teaspoon of water to form a paste. Another option is to mix 1 teaspoon of salt with a few drops of water. A ready-made polish you can use for this task is non-gel toothpaste.
Dip a clean, soft cloth into the polish and use it to rub the polish onto the water stain.
Wipe off the polish with a damp cloth.
Shine the baseboard with furniture polish.