After a few years of daily use, the minerals in water—not to mention dirt and grime can make any tub look stained and dingy. Instead of reaching for some harsh chemicals, mix up equal amounts of baking soda and cream of tartar (found in your grocery's spice section) with lemon juice until it forms a paste. Apply to stains and rub in, then wait about an hour and rinse. For tougher stains, leave on for an hour and rinse well.