Basically it's a self-directed ceremonial magickal practice with Satan as the central deity. I discovered it through Chaos Magick and Thelema (I was dating a woman who was a Thelemite at the time). I believed Satan, or Lucifer -- I generally equated the two -- embodied individuality, free thought, and self-directed spirituality. I didn't even like to say I "worshiped' Satan because Satan found supplication or worship to devalue the individual. Instead I said I "revered" Satan. There was no selling your soul to the Devil (your soul was your true self and you had an inherent right to it), no animal sacrifice, nothing like that. I liked a particular book (which I can't find anymore) that described a spiritual journey whereby a Satanist could spiritually travel to a separate plane of existence that was totally untouched by god. Essentially, God was a tyrant, Satan was the liberator. Your spiritual journey was truly your own, and the goal was to be liberated from any spiritual restraint or confines, thus realizing your true self. That's the long and short of it.
I don't believe that stuff anymore. Haven't for many years. Now I believe that when you die, you're dead, the end. Throughout my life I've experimented with all kinds of things: raised Catholic, became atheist in high school, converted to Methodism in college, dabbled in Hinduism, then was a Satanist, then a Wiccan, then an atheist. I liked to explore. Nowadays I find religion pretty dull. I'm satisfied with a shrug, an "I dunno, but probably nothing," and enjoying life as I see fit. Still feel some sympathy for the devil though, especially in discussions like this thread.
Satanism was a bit too confrontational and aggressive for me. These days I find a lot of inspiration and comfort in nature, particularly birdwatching. That's where I experience what some people might call "spirituality." It was a phase I went through. I'm glad I did, but now I'm over it.
