Start with a corrector, a cream-based formula that brightens up discoloration under the eyes, either in a pinkish tone (if your skin tone falls somewhere between Gwyneth Paltrow's and J. Lo's) or a peachy shade (if you're darker than J. Lo). Then, right over that, apply concealer that's one to two shades lighter than your skin.
Those two steps together will make dark circles disappear, but the reason Alexis looks so evened-out in her "after" shot is that I followed up with a tinted moisturizer. I like it instead of foundation because it gives enough coverage, but you can still see her skin. To find your right shade, apply it to your cheek. If it disappears, you've met your match!