Anyway. Superstitions are all in your head. They don't exist in the 'real' world... but that doesn't mean you cant control it. It is human nature, so make it work for you.
The superstitions are always negative, "Don't do this or you will have bad luck", or "If you do this you will die". They also only work by you noticing the results, so if you break a mirror, if anything bad happens you will remember breaking the mirror. If anything good happens then you don't. Next time you think of that mirror you will associate it with all the bad things that followed.
To create a superstition you must associate an action with a consequence. It also maybe helps to rationalise it.
I don't strictly believe this, but if you convince yourself you do then it works... everything has a 'luck' factor. The luck is absorbed by people as they pass it. Getting on the bus gives no luck, as everyone does it, neither does walking past a black car.
People maybe don't notice, but I make sure to walk under every post/ladder around. It has lead to unnatural slaloms throughout town centres, that would look only more natural if my tongue was hanging out, complete with a small bit of dribble. This means I get to steal all the luck, because other people avoid it, making me lucky for the whole day!
The same logic** can be applied to anything. So get walking on those cracks!
Oh... and that a kid eating a cat. I don't know why.
** Logic probably isn't the best choice of words.