How do you get rid of dark circles under the eyes?

I often get dark circles under my eyes, and not only when I'm very tired. I'm a little concerned as to why this happens and what it means when it does. But more than anything I just want to get rid of them, ideally without involving anything too drastic. Are there measures I can take to stop them from forming in the first place? And failing that, anything a doctor could do to permanently remove them and make sure they never come back again? Thank you.