Stains need to be cleaned up as soon as possible using standard wood cleaner. Many stains will be removed by this process if done soon after the stain occurs.
Remove white stains and water marks by placing a cotton cloth over the stain. Using a dry iron with no steam, press down on the cloth for several seconds. Remove the cloth and inspect the stain. Repeat until the watermarks are gone.
Remove white stains as well as some darker stains by rubbing them with a rag soaked in mineral spirits. You may need to rub for several minutes. Mineral spirits will remove the wax on the furniture without harming the finish. The area will look dull when finished, but this can be resolved by adding a coat of furniture wax.
Remove crayon from your wood furniture with toothpaste (not gel). Rub the toothpaste on the mark with a damp cloth. You can also try using a mixture of 50 percent toothpaste and 50 percent baking soda, which is said to also remove white water stains.