There are eye makeup removers, and if your mascara is waterproof you'd probably be better off using something made to take it off.
If it isn't, I'd just use whatever face cream you use. Wash with soap and water as you normally do, then dab the face cream under your eyes and gently wipe it off. The mascara should come with it.
The stuff I use is for dry skin, so it's probably oilier than some others.
If that doesn't work, a friend of mine uses plain old witch hazel on a cotton swab.
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