Good luck:
A horseshoe over the door brings good luck.
It's lucky to meet a black cat, to touch wood, to find a clover plant with four leaves, to catch falling leaves in autumn.
For good luck the bride should wear “something borrowed, something blue, something old and something new”.
Bad luck:
It's unlucky to open an umbrella in doors, to spill salt, to break a mirror, to walk underneath a ladder, to see one magpie (it's lucky to see two magpies).