The birthday person should make the first cut in the birthday cake, making a silent wish while cutting.
(Pennsylvania)
When it's time to cut the wedding cake, the newlyweds should both put their hands on the knife as they make the first cut; each should make a silent wish while cutting.
If you put a piece of wedding cake under your pillow, you may wish on it last thing at night and repeat the wish first thing in the morning, provided you have not spoken to anyone during that time.
Some say you will have good luck if you sleep with wedding cake under your pillow, and others say you will dream of a future love.