If you know you're going to be moving from a well-lit area to the dark, you can cover one of your eyes — like a pirate with an eye patch — for a few minutes beforehand to see better in the dark.
Photo by emberflylayouts.
It's long been speculated that pirates and sailors would wear eye patches so they could see better below deck. They'd keep the eye patch on in the light, then when they went into the dark, they switched the eye patch over to the other eye. The one that had been under the eye patch for a while would be well adjusted to the dark and they'd be able to see much better.
You can use this trick in your daily life, if you know you need to enter a dark area (say, a basement with no lights in it). Just cover up one of your eyes for a few minutes beforehand (or throw on an eye patch, if you're feeling rather piratey) and head down into the dark. If you open your eye and close the other one, you should be able to see better. This tip's been floating around the internet for a while (it was mentioned on Mythbusters), but after a reminder from Redditor VerticalZero, we thought it was worth featuring. Hit the link to see more.