To all the 'brush your teeth' people, that's a bit unrealistic.  Teeth naturally come in different shades.  You could be the most hygenic person in the world, and not drink coffee or smoke, and still have yellow teeth.
As for suggestions to whiten -- crest whitestrips are supposed to work the best of the off-the-shelf options.  I've had friends attest to this.  You can also get professional grade crest whitestrips from your dentist.