The etymology is from the classical Latin superstitio, literally "a standing over", hence: "amazement, wonder, dread, especially of the divine or supernatural". The word is attested in the 1st century BC, notably in Cicero, Livy, Ovid, in the meaning of an unreasonable or excessive belief in fear or magic, especially foreign or fantastical ideas. By the 1st century AD, it came to refer to "religious awe, sanctity; a religious rite" more generally.
I love Heather's definition - that ritual is based in love, and superstition in fear.
And to that (neurotic) end, I do have a few superstitions about writing. I don't really get into the details of the plot of any story I'm working on with anyone until I'm well into it. Or, many times, with myself (hee).
I'm guessing superstitions are as different as writers. I'll admit to being superstitious about the query process as well - that is, I'll say a little prayer over an envelope before I send it, I'll consider the day and whether or not it might be auspicious, and most of all, I don't tell anyone I know anymore about when I query and what the results are.
So, what are your superstitions when it comes to writing and creating?
Please, have some Stevie Wonder, live on Sesame Street. You're welcome.