Throw a coin into a fountain while making your wish.

Throw a coin into a fountain and make a wish. Count the number of rings it makes on the water's surface. If it is an even number, your wish will come true. If there are an odd number of rings, your wish will not come true. Throw a coin into a fountain and make a wish. After making your wish, look for your reflection in the pool. If you see it, there's a better chance that your wish will be granted.

Throw a penny into a fountain (it must be a penny, not some other coin) and wait until the water has stopped rippling and you can see your reflection before you make your wish.

With your back to a fountain, throw three coins over your head and into the water. With each splash you hear, repeat the same wish. If you hear all three splashes, the wish power in the fountain is strong for you.
(Europe)