1. If you use foundation, apply it first, and then apply your concealer.
If you apply your foundation first, you'll find that you don't need to use as much concealer. If you apply concealer first, however, you'll remove most of it while applying your foundation.
2. The most flattering way to apply concealer is to draw a triangle with the base under your eye and the point toward your cheek.
This shape not only conceals dark circles, but it also instantly creates the illusion that your face is lifted. Think of it as holding a flashlight against your cheek, shining the light right underneath your eye, and drawing the focus upward.