Here's an insider opinion from a man claiming to have spent 8 years as a satanist with the rank of Priest within their system.
Essentially, satanism is about being a douchebag and taking advantage of others instead of respecting them as one would oneself - being a 'douchebag' including such acts as staging the 9/11 false flag ritual and starting wars for profit. An ideology of unbalanced egoism, ungratefulness, malice and self-deceit and rejection of the laws of the very Creator who caused one to exist in the first place.
Of course, there will be all sorts of excuses made for why satanism is actually a really good idea and people really need to look into it and such. How it's actually a religion of understanding, enlightenment and sound humanitarian values etc. You need look no further than the picture below to understand all you need to know about this 'ideology', though.
... essentially, if you can't be bothered to take responsibility for yourself and commit to the path of righteousness, abstinence from wrongful temptations and the hard work of self-improvement just declare yourself a satanist and delude yourself into thinking you somehow can supercede almighty God's eternal laws and won't be held responsible for having done so.