I've had a problem with dark under-eye circles since I was in college. It's a mixture of natural coloring, I think, and the amount of sleep I've been getting and how hydrated I am. Sometimes they get a little better, but most of the time (probably due to my general refusal to sleep for 8 hours each night), they're so dark I have to hide them before I walk out of the house every day.
I went to the Bobbi Brown counter looking for concealer because I'd heard theirs was phenomenal. I ended up buying their corrector, concealer kit and their concealer brush. All three were a hefty $82.00, but they were well worth it considering that they really work and the amazing advice their representative gave me for applying the concealer. It goes against everything I ever thought when it comes to concealer application, but it absolutely works. While I still have the dark circles, they're concealed so effectively, they're invisible for hours!
Want to know how?
** Warning: the following photos contain graphic material of Jen without her makeup on.

The Bobbi Brown representative told me to always start with a generous dose of a good quality eye moisturizer. I've been using my Shiseido Under-Eye BioContour Cream and have had excellent results. Make sure that the undereye is thoroughly moisturized before continuing.
The next step is corrector. This is the first time that I've ever purchased a separate corrector, and it's amazing. It does most of the heavy lifting. Use your concealer brush to paint on the corrector until you can no longer see your dark circles at all. Paint up the side of your nose toward your brow, and don't be afraid to use concealer well beyond the outer corner of your eye. If you're following along right now, you're thinking, "I look like a clown." Well, yes you do, but it will all be worth it soon enough.

Give that a few minutes to soak in. It will plump up the fine lines under your eye and very nearly cover any darkness under your eye, but mainly, we're going to use this as a primer for your concealer. You don't really need to blend the corrector into your skin, but you will want to smooth the corrector at the corner of your eyes so that it blends in with your skintone.

Now, apply a layer of concealer with the brush. Don't be afraid to use a lot. Sparingly doesn't conceal well. After you've completely coated your undereyes with the concealer, wait about 10 minutes before you touch your undereyes again. So go walk the dog or just style your hair, anything to allow the conealer time to soak in without any micro-managing.
When the time is up, go ahead and apply your foundation on the reddest areas of your face. Work the foundation line into the concealer line until completely blended. Don't smear the makeup or smooth it in. You want to press the foundation and the concealer into each other and into your face in order for your makeup to look like it's your own natural skin.
After you've pressed the concealer under your eyes lightly, you might want to follow with the light yellow powder that accompanies the concealer in the concealer kit. The yellow powder will keep you from looking shiny in pictures, but it also will dry you out. If you've got dry skin and you aren't going to be in any pictures, you can skip this step entirely. I generally do.

Voila! Flawless concealer coverage. If you see yourself in the mirror later in the day and it looks less than perfect, you can usually revive the look by pressing lightly on the concealer. The picture to the right was taken after I added foundation and blended with my concealer. See? No circles!
Hopefully this will change your life like it did mine. When I told a friend at work recently about my concealer miracle, she responded, "you don't even have dark under-eye circles!" That's when I knew beyond a doubt that this miracle was worth sharing with our DeLush readers.
By the way, the steps I've outlined work for any brand where a corrector and concealer are offered. I've used the same application technique with my Revlon concealer duo, applying the pink and then working in the more yellow shade and gotten very good results. While I may use other brands on the weekends, the Bobbi Brown really is superior and is always my choice for work.