Jews do not believe in superstition, per se. In fact, it is forbidden for Jews to behave in a way that indicates they are afraid of something that is based on superstition, like a black cat or walking under a ladder.
However, there are discussions in the Talmud that deal with things that should be avoided. Jewish culture acknowledges such phenomenon as Mazel, which is loosely defined as a force that affects people in different ways, sometimes stemming from the moment in time when they were born. There are propitious times in the Jewish calendar, times when good things will happen, and times when not-such-good things will happen. There are foods that are believed to cause spiritual decline, and/or physical illness. There are times and places, where the Talmud states that "evil spirits" are rampant. Sometimes things are done an odd number of times because "pairs" are to be avoided. Presumably, the origins and basis for most of these beliefs came from events and experiences of the early sages, and from Scriptural derivations that arose from their discussions. Those who are aware of these restrictions tend to avoid them as much as possible, without seriously disrupting their lives. Sometimes, it isn't practical to keep them all in mind, and people just do what they can.
