As the legend of the 4-leaf clover goes, when Adam and Eve were kicked out of the Garden of Eden (paradise) Eve took a 4 leaf clover with her as a souvenir of what they once had. So, if you are lucky enough to find one it is considered to be something a piece of paradise.
HORSESHOE
The development of the horseshoe proved to be a huge advantage in battle. It is believed that the Greeks began shoeing their horses almost 3000 years ago. This protected their horses which led to better health for the horses, but more importantly better stability in battle. They believed that the shoes brought them good fortune in battle (it actually gave their horses better stability which led to more victories). Today, people hang horseshoes in their homes in hopes that some of that same good luck afforded to the Greeks will come their way too. (Don't hang it the wrong way or all of the good luck will run out of it).
FENG SHUI
Feng Shui is an ancient Chinese system of aesthetics and arrangement. By properly arranging and organizing your home and furnishing it with the correct pieces you will help to promote positive QI (life force). A small example of Feng Shui, if you have an aquarium you should always have an odd number of fish. One of the fish is used as a talisman to absorb negative energy and prevent disaster. If one of the fish dies one should rejoice because the fish has sacrificed itself to prevent a disaster in the household.