If you spill salt, you must take some and throw it behind you so you wont be unlucky.
My informant first heard about this superstition while he was watching a movie. He was watching the movie Just My Luck starring Lindsay Lohan. In the movie, Lindsay Lohan is the luckiest girl in the world. However, she meets a really unlucky guy and through a kiss their luck switches. Lindsay Lohan becomes really unlucky and while she is in a restaurant she spills salt. To not get bad luck, she takes some of the salt and throws it over her shoulders.
Salt is associated with a lot of symbolism and superstition. In ancient societies, salt was very expensive to buy and was a very precious product. Salt is used as a preservative and in someway began to symbolize life. Salt also became a sign of hospitality, trust and friendship because of how expensive it was. Therefore to spill salt was a waste and many people believed that bad luck came to the person who spilled it. Some people also believed that if salt was spilt in a particular persons direction then bad luck would come to that person. Some people throw salt over their shoulders. However, salt must be tossed over their left shoulder and into the face of the Devil. Therefore, spilt salt should never be cleaned up. Some people also believed that enough tears must be cried to dissolve the spilt salt. This would reverse the bad luck that was coming to the person. Another superstition for salt is that salt is thrown on the threshold of a new house for good luck.