Satanism is generally misunderstood due to its very
grandstanding name. If you consider the Church of Satan founded by Anton Szander LaVey, it seems to be more about accepting human nature and not messing in the affairs of others than about worshipping "the devil". There are a few smaller denominations that actually are about worshipping the devil, and I would say they fall into two categories.
The first category is of those that generally follow the priniciples of the Church of Satan, but disagree with the atheistic/agnostic stance of the church.
The second category is the very rare group of people that burn down churches, cut themselves, possess body parts, murder people etc etc. One of them is the Temple of the Black Light. These are probably the satanists you are thinking of.
So to sum up, most satanists do not worship "the devil", they worship the human nature and see satan as a symbol of liberation and self acceptance.
These people follow satanism because they feel it is an honest way of life which also includes respect for other people.
There are no banworthy practices among these satanists.