Whitening always makes me think of Erik Estrada in Chip's Patrol, better known as Poncherello.  Teeth so white you can't tell where one ends and another begins.  Seriously, though, there are several options for whitening.  You can do it yourself with take-home kits that use either universal or custom fit trays.  This method typically takes about two weeks.   Application is in two hour increments or overnight.  This is the better option for those of you with sensitive teeth and a higher level of patience.  You can also risk the pain of in-office whitening that is done in 15 minute increments, a better option for less sensitive teeth combined with an "I want results now" attitude.  Both work well and can improve two or three shades with each application.  Any method will lessen over time and must be maintained or repeated to keep those whites pearly.  I use Opalescence products.  Check it out at opalescence.com if you want to learn more.