"When creating a cheekbone," said Rob, "the color should graduate. You need to blend so lines aren't sharp." First, find the hollows of your cheekbone using the handle of a makeup brush or the side of your hand. Using the Tweezerman Brush iQ Pointed Foundation Brush ($22), start creating your contour line from your ear to under the apples of your cheeks. (The color should be darkest closest to your hairline.) End your line by creating a lightly sketched "little Nike swoosh" under the apple of your cheek.
That said, when asked how he decides where to stop contouring under the cheekbone, Rob said it depends on your mood. "If you want, you can continue the line down the side of the chin," he said, which will create a very chiseled, vampy look.