To cut down on the spread of germs, greet friends with a fist bump.

Why: In a study, researchers wearing gloves dipped in bacteria transferred 10 times more germs while shaking hands than when they used the knuckle greeting. Other microorganisms, such as cold and flu viruses, are also spread this way.

Reason: A handshake lasts longer than a fist bump, and more surface area of the hand is touched.