Put cucumber slices on them .. it does work.
Mostly though .. get lots of sleep and drink plenty of water .. stay healthy!
Wear a bag with a smilly face on it.
Sometimes the dark circles are genetic and there is nothing you can do short of covering them.
However, do you have allergies and/or sinus problems? Are you getting enough sleep? These things can really affect the area beneath your eyes, especially sinus infections. When I was a kid I had terrible dark circles much of the time due to recurrent sinus infections.