Without concealer, I look like Uncle Fester. Ergo, concealer is my friend. My very, very good friend. Once you know how to conceal dark circles, you're well on your way to looking like you've just had a full night's sleep.
But here's a little trick to look not just well-rested, but absolutely glowing. After applying concealer, dab a few drops of liquid luminizer (such as Smashbox Artificial Light) underneath your eyes, moving to the outer corners of your eyes, and near the brow line. You don't need much, and the idea is to pat and dab the luminizer rather than rub it in. The light-reflecting pigments will bounce light off of your skin, making your entire eye area appear brighter — and you'll look 100% bright-eyed and bushy-tailed. (OK, maybe not bushy-tailed, but one out of two isn't bad.)