We tend to be superstitious but I think superstition in more demographic than pagan!
There are a lot of beliefs in witchcraft that are considered superstitious, but many of the superstitions associated with witchcraft have roots in other religions. Take the resent Friday the 13th. Many people don't even remember why this day is considered bad luck! The number 13 in Christian beliefs was considered unlucky due to the thirteenth guest at the last super. Judas. It was Judas who betrayed Jesus at the last super with a kiss and led to his crucifixion. So the number thirteen was avoided. Fridays were the date that the Church came around to collect taxes and dues. If you didn't have them then they would take what you had as payment. Combining the two superstitions only made sense that it was an unlucky date! I guess for people like Tupac Shakur and Julia Child it was a pretty unlucky date.
The poor black cat is another! It has it's roots in Christian and Witchcraft. During the witch hysteria in Europe stray cats were cared for by poor old women who stood out and were eventually accused of witchcraft. The cats were guilty by association. Black is the most common color for a stray cat. However in countries like Japan and Egypt black cats are considered GOOD luck!
Breaking mirrors or spilling salt were considered bad just because these were expensive items to own and hard to replace. Throwing salt over your left shoulder is however a Christian belief. It was believed that spilling salt was your guardian angel warning of the devil on your left shoulder's intention for mischief. If you throw a pinch of salt over that shoulder you throw it in the devil's eye and he can't do his mischief!
Knocking on wood traces back to early Christian beliefs. The cross that Christ was crucified on was made of wood. So wood was considered blessed with good luck and good spirits watched over it. Knocking on it was asking these spirits for some of that luck!
Sure witches have their own superstitions as well. If the broom falls over or a bee flies in your home, company is coming. If you throw back the first fish you catch as an offering to the spirit of the lake your day fishing will be fertile! Crossing door steps with salt wards off evil. If a woman is pregnant and over due the full moon will encourage her baby to be born.
For what ever reason you have a superstition it was more likely caused by the place you live. A large variety of superstitions are considered "Old World" or "Deep South". Many of them are superstitions passed down culturally from one parent to the next! Many of the Deep South superstitions originate from a collection of cultural mixes of poor southern farmers, the African slaves, and the blend of ethnic diversity between the people of these areas. Many are a combination of beliefs from all the different people and religions.
Many superstitions are based on real things. Going out at night could be dangerous. Many bad people use the limited visibility of the dark to do things without being seen. Bees in the garden do help it grow by spreading pollen around to help the plants out! So definitely plant sunflowers for a good harvest! Try lighting three of anything with the same match you'll definitely find it a bad idea!!!