Teeth Whitening

We know toothpastes that claim to make teeth whiter are lies. I want to get my teeth professionally whitened (laser??)
Does anyone have any more info about professional teeth whitening? Like what celebrities do? Prices? Different procedures?The first step to understanding ‘whitening’ is how to measure it.

There is something called a ’shade guide’, which is often used to measure the coloration of teeth. This is best done by taking the various shades and putting them next to your teeth until the color most closely matches the teeth.

My friend brushes her teeth twice a day, and always has since I’ve known her, but for some reason she has off white-slightly yellowish teeth. Her family doesn’t have a lot of money and she can’t afford to go to the dentists. What would be the most effective and cheapest method for whitening her teeth?