Breaking a mirror: many years of bad luck.
It could cause your body and soul to become separated. There was a belief that a body changed composition every seven years; hence, it was thought that a broken mirror would bring seven years of bad luck. After those seven years, you could start over with a clean slate.
Spilling salt: bad luck.
According to superstition, the bad luck caused by spilling salt can be averted by throwing a little over your left shoulder. That's where the devil resides, and if the salt gets in his eyes, he'll be blinded.
More bad luck:
Walking under a ladder.
Friday the 13th.