Once a wedding ring has been placed on the finger, it is considered bad luck to remove it.
117
Many believe that if all of the candles on a birthday cake are blown out with one breath, while making a silent wish, the wish will come true.
298
Placing keys on a table is considered unlucky. (Sweden)
3
If one walks underneath an open ladder it is said to bring bad luck. Sometimes it is said that this can be undone by immediately walking backwards back underneath the ladder.
105
An acorn should be carried to bring luck and ensure a long life.
115
It is bad luck to put new shoes on a bed (or a table) (comes from the tradition of dressing a corpse in new clothes and shoes and laying them out so everyone can give their respects) - (UK)
57
When you speak of bad luck, it is said that one should always knock on wood. Also knocking when speaking of good luck apparently helps with having good luck. This is an old Celtic tradition related to belief of wood spirits.
208
It's bad luck to leave a house through a different door than the one used to come into it.
143