Placing a hat on the bed is, apparently, bad luck. (South Carolina)
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)
Once a wedding ring has been placed on the finger, it is considered bad luck to remove it.
Pirates believed that piercing the ears with such precious metals as silver and gold improved one's eyesight.
Placing keys on a table is considered unlucky. (Sweden)
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.
It's bad luck to leave a house through a different door than the one used to come into it.
Opening an umbrella indoors is said to result in 21 days of bad luck. Some traditions hold that it is only bad luck if the umbrella is placed over the head of someone while indoors.