I don't seriously expect a death in the family if I bring hawthorn flowers into the house or open an umbrella indoors, but I don't habitually do so, so perhaps at the unconscious level I do believe in the superstitions.
I sweep dust up into a dustpan, never straight out the door and would dislike it intensely if a visitor at Christmas didn't either eat or drink something offered them before leaving again.
I grew up with most of the superstitions mentioned in this thread, and would still put a coin or a bank-note into a purse or wallet I intended giving someone as a present.
My father insisted that a gift like a knife, which can cut, or a brooch that can stick into someone, should be "paid" for when given as a present, by the recipient handing over the smallest coin of the realm. This prevents the friendship being cut or damaged by the gift.