i don't know about making your skin actually whiter, but exfoliating your face and body often is really good for keeping your skin at your natural tone (scrubs off old skin cells and skin that has tanned, yknow :'))
you can either invest in a good scrubbing cloth or get one of those exfoliating soaps (i've tried tokyo love soap, koji acid soaps, etc., and they're all pretty good- just follow the instructions carefully)
hope that helped