One thing that almost all cultures have in common is wishing good luck to newly-married couples, because they are going to need all the help they can get. It's no wonder that so many superstitions have grown up around weddings. Something odd happened at Sven and Gerta's wedding and they are miserable, so that must have been bad luck. Something else happened at Johann and Eve's wedding, and they have six children now, so that must be good luck. If it worked once, it may work again, and so a tradition begins.
1. IN GREECE, THE BRIDE AND GROOM GO NUTS WITH SNACKS.
The Mediterranean country is home to a sweet tradition. The happy couple hand out sugar-coated almonds, called koufeta, to their guests. As one Greek Orthodox bride explained to Manhattan Bride magazine, the white of the almond symbolizes purity, the egg shape is a sign of fertility, the hardness represents the endurance of marriage, and the sugar is meant to show the sweetness of married life. Together, they’re meant to wish the newly married duo "happiness, health, wealth, children, and a long life." And should a single girl take one of the blessed snacks and sleep with it under her pillow for three nights, tradition states she’ll somehow see her future husband!
Read about ten more wedding superstitions at Mental Floss.