All cultures have superstitions
One of the most common criticisms outsiders make of Santería is that it's full of superstitions, and practitioners of the religion are superstitious people.  For many Christians, it's a sin to be superstitious because it challenges the idea that God alone has the power to shape our lives.  This isn't a very logical argument if you look at it closely.  First of all, the teachings of Santería tell us that there is one Supreme God who has three forms, much like the Holy Trinity of the Christian faith:  Olodumare, Olorun, and Olofi are the names of God in this religion.  People who practice Santería believe that God has control over everything in the cosmos.  Concepts like free will and destiny are complicated metaphysical ideas that aren't easily explained, but in the most general terms, we can say that practitioners of Santería believe that everything happens for a reason known only to God, we have some control over how things turn out in our own lives and can influence our destiny through our behavior and the choices we make in life, the Orichás and the egun (spirits of the ancestors) can intervene on our behalf and guide us toward evolution, and those who have the happiest and healthiest lives are those who live in harmony with the destiny that corresponds to them on earth.

Are these superstitions?  The definition of superstition is a belief or notion that is not based on reason or knowledge, an irrational fear of what is unknown or mysterious (especially in connection with religion), or any blindly accepted belief or notion.  All religions require people to have faith, and to accept dogma that explains the basic tenets of the religion.  These ideas aren't necessarily based on reason or scientific knowledge.  At the risk of upsetting people who are deeply committed to the Judeo-Christian tradition, I'll point out that there are many stories in the Bible that defy rational explanation.  People who believe that God passed down the Ten Commandments to Moses, or the Virgin Mary gave birth to the son of God believe that these things are true, even if they are not based on scientific "reason" or "knowledge." These ideas are based on beliefs, and are held to be true by people who have faith in the teachings of their religion.  Santeria is no different, because it also has a system of beliefs that has been passed down from the ancestors, and these beliefs have been considered sacred and holy by many people over the course of many years.

Divination, for example, is not a superstition for practitioners of Santería, but a sacred ritual.  The advice that comes from the Orichás and the egun is divine communication, not fortune telling. The Lucumí people believe that God doesn't speak directly to humans because we don't have the ability or understanding to grasp the complexities of God.  The Orichás and egun are closer to us on earth, and can help guide us toward the right path in life. They know God's plans for us, and they can help us understand those plans a little better.  We communicate with them through divination, trance possessions, drumming and dancing ceremonies, prayers and songs.  Sometimes we carry out other ceremonies like the rogación de cabeza (spiritual head cleansing), we make ebó (tributes, offerings), or we receive additional elekes (beaded necklaces) or prendas (amulets) to protect us or help us evolve. To outsiders, it may seem that these are superstitions, but from inside the religion, they are sacred ceremonies, based on a traditional and ancient system of beliefs.  They are visible manifestations of faith.

Who has the power to cast spells?
The area where things get a little  more shady are the trabajitos (the little spells or 'works') that some practitioners do to influence the behavior or attitudes of the Orichás and egun.  For example, it's commonly believed that putting a clear glass of water under the bed while you sleep will keep away troublesome egun in the night, who might otherwise disturb you when you sleep.  People who suffer from bad dreams or involuntary twitching while asleep might be diagnosed as having a problem with "un muerto" (spirit of the dead) and told to sprinkle themselves with cologne and cascarilla (powdered eggshell) before going to bed.  Are these superstitions?  I prefer to think of them more as folk wisdom.  The belief in egun is fundamental to Santería; for practitioners of the religion there's no doubt that egun roam the earth and interact with the living.   Egun are not the same as ghosts. They don't inspire irrational fear.  Many egun are friendly and act as guardian spirits.  But, the egun need to be kept under control, they can't be allowed to interfere too much with our lives, because even without meaning us harm, they can start to rob of us health, prosperity, and other things we need and desire to live well.  Generation after generation, people have passed down recipes and remedies to help people deal with these problems that crop up in daily life.  Perhaps the effect is merely psychological, but psychological remedies can trigger the subconscious mind into new patterns of thinking that can relieve bad dreams or anxiety in some people.  Studies have shown that there's a connection between what we believe to be true and what we experience as true.

Mainly due to the influence of the media and popular culture, many people think Santería is all about curses and spells and witchcraft.  Many people outside the religion have an irrational fear of it because they associate it with powers they don't understand.  It's important to note that in most cases, these fears are based on misinformation and a lack of clarity about the religion.  Do you have bad luck because you have been cursed by someone?  Or, do you have bad luck because you made bad choices, acted unwisely, engaged in risky behavior, or otherwise brought bad luck into your own life?  Did you lose your boyfriend because someone put a spell on him? Or did you lose him because you were difficult, demanding, unreasonable, or neglectful?  Sometimes people are hesitant to take responsibilities for their own actions, and quickly look for a scapegoat to carry the blame. It's easier to say that someone put a spell on you and caused you to fail rather than examine your own actions to see if you did something wrong. 

Other times, we encounter obstacles and problems that have no apparent cause.  Clearly, we aren't always to blame for what happens to us, and it's natural to look for an explanation outside ourselves.  These obstacles manifest themselves in the physical world as osorbo (blockages, obstacles) that can have many causes and origins.  They may be sent by God or the Orichás to challenge us to change something about ourselves or our circumstances. They may be caused by gossip and envious people who send bad energy to us.  Ogo (witchcraft) does exist as a possible source of osorbo, but it's not the only one, nor is it necessarily the most common one.  Through consultas (divination sessions), ebó, and protective measures one can avoid or remedy problems caused by ogo.  The situations represented in television shows, movies and popular novels where people die as a result of a Santería curse is a distortion and misrepresentation of the religion. 

So, in the end, we have to ask: where does superstition come into the picture?  In order for a spell or curse to work, there has to be belief on both sides:  the one who does the spell has to believe it's real, as does the one it's aimed at.  People who fear Santería as a religion that can harm them must on some level believe it has the power to do harm.  Are they being superstitious? I would say yes, because their fear is irrational, based on something they don't understand.  People who practice Santería as a religion believe that it has the power to help them, and on some level, their faith is what makes evolution and progress possible.  The difference between belief and superstition, then, depends on the point of view of the person speaking.  Insiders understand and accept the beliefs of the religion, and their faith allows them to accept the beliefs as true, despite the absence of logical explanations and scientific knowledge.  Outsiders feel doubt and sometimes fear, because they don't understand the underlying principles of the religion.  The next time we criticize someone as being "superstitious," we need to think about the difference between superstitions and beliefs, and ask if our choice of words reveals cultural narrow-mindedness.