Depends on who you ask.
Most people follow LeVey's belief system, but I think that for the most part, thats a bunch of bull. The system is plagued with pompous arrogant, unfounded beliefs, seemingly just to stroke the ego of the anti-Christian, and shelter the believer in a safehouse of sorts. Its a waste.
My ideology of Satanism is defiance. The ideology of one of the most blessed angels, Satan, being cast aside merely because of the newborn creation, man, by a materialistic, tyrannical overlord, G*d, is quite the novel idea. Satan defied G*d, when he told Satan, the one time apple in the eye of the Lord, to bow down before the new creation, and I find that ideology incredibly attractive. G*d looked over the angels in favor of the new creation. What happens when G*d creates something else? My guess is humans will take second place, in favor of the newer beings, just as he did with the angels. Its unfair, and Satan rebelled against that.
The rebellion and defiance of an unjust overseer is what attracts me to the belief system, and its that rebellion that lets me be strong in my everyday battles. I think its a nice little cushiony system of beliefs for a person like me in the life I live.
I'm also a flagship of clearing up the confusion of Lucifer and Satan. Lucifer did not become Satan when he was cast out, Lucifer is his own angel. Lucifer's name translates as 'son of light', and the reason Lucifer was banned from heaven, was because of G*d's mistake. He mistakingly made Lucifer as smart, powerful, and divine as himself. Lucifer is more or less the exact image and reflection of the G*d before him, and because of the Lord's little di-er...oversized ego, he banned him. Funny thing though, Lucifer still retains his power in heaven, and influence over Micheal, and the other arch angels. If ever the battle of Armageddon did come, Lucifer would be the Supreme Allied Commander in the army of the angels. The thing is, Lucifer has no interest in G*d's heaven, and has since *according to the stories and legends, mind you* created his own cosmos, and basically has a whole new life that nobody talks about.