To polish brass, use Worcestershire sauce; or pour on ketchup, let sit, then wipe dry.
To clean chrome, just use baking soda and a dry cloth.
To polish chrome, rub wet fixtures with newspaper or rub with baby oil and a soft cloth.
To polish copper, pour vinegar or lemon juice and salt over copper and rub. Rinse thoroughly and dry.
To polish stainless steel, clean and polish with a baking soda/water paste.