Just for the people who don't know me that well: I am a Satanist. Unfortunately, that label has a lot of stigmas attached to it. A friend of mine once wrote this small essay about this very subject, and I tend to agree with the definitions used therein. For the people who don't like to read large pieces of text, a small abridged version:

• I don't believe in gods, and therefore also not in devils. So to equate Satanism with devil-worship is plainly uninformed stupidity.
• I don't believe in an afterlife.
• I do not put much value in fantasies like spirits, ghosts and other new-age claptrap.
• I don' t worship anything but myself.
• I do not drink blood.
• I do not sacrifice or harm animals or humans.
• As an exception to the above statement, I will kill/maim/harm in self defense or to protect what I hold dear.
• I couldn't care less about your or anyones gender-preference.
• I am capable of love, hell, I'm married to a woman I love dearly.
• I am also very capable of hate. And I don't make a secret of that.
• Yes, I am an egoist. I do place myself first in all decisions that I make.
• Yes, I am sceptical about all religions, even my own (Satanism).
• Yes, I do practice Satanic magic. (Confused? Read on)

Still curious? Ok. If you want to know more, read on.

Satanism (c) 2007 Bob Ferguson

Satan, a word from the Standard Hebrew Satan שָׂטָן and the Aramaic Shaitan, סטנא .
The name is also found in Arabic, Shaitan شيطان
The word "Shaitan/Satan" finds it's root in the Northwest Semitic word "STN" which can be defined as meaning to "accuse" or an "Adversary."

Also, As is revealed in the book of Job אִיּוֹב found in the Tanakh, which is what christians have come to understand as the "old testament"
When G-d asks the angel who was a Satan from whence he came, his response is;
"From wandering the earth and walking on it" or in the Hebrew; מִשּׁוּט בָּאָרֶץ, וּמֵהִתְהַלֵּךְ בָּה
In this regard, Satan the is also a wanderer, one who has chosen to be of the earth, part of it.

This brings us to the understanding of the Philosophy, and to some the Religion of Satanism.

Satanism and Satanists

Satanism is the Philosophy/Religion that advocates the centrality of Humanity as the origin of the divine mind.
With the individual standing as an accuser, or adversary to any system, theological or Secular that seeks to limit the natural self determination of a Human being. A Satanists also chooses to exist within the world, not removing him or herself from it. They allow themselves to be a part of the natural order while at the same time understanding that their mind can achieve acts of thought which transcend much, but not all of the established instinct structure. Yet the Satanist still remains part of the natural current of the cosmic order.

Because of this philosophy, Most all Satanists can be placed into a few minor categories, each categorie differs in minor and sometimes major ways in regards to the philosophical approach of the adherent.

1. The Atheist Satanist, who chooses to believe that there is no divine creator who gave us a divine mind. It was the strength of the Human ape and our ability to evolve that allowed us to develop what is now known as Higher conciousness, Sentience, self awareness, and the ability to communicate such concepts.
    
2. The Deistic or Agnostic Satanist, who might hold to the belief that we do or may have come from a divine awareness, but that awareness is impersonal and does not involve itself in the affairs of our Cosmic order. In fact, many Deist Satanists hold that even our own planet was not the personal creaton of this Divine conciousness and that what is more probable is that this Overmind created the initial sparks of our cosmos, only to remove itself from the process once the initial spark of creation was struck.As a result, the personal outlook of a Deistic Satanist and an Atheistic Satanist in regards to Magick and the various Mythology of the Gods of man would be very similar, if not the same.
    
3. The Theistic Satanist, a Theistic Satanist will be more Pantheistic, accepting that Satan is a common creator deity with many names throughout history. Theistic Satanists have been known to recognize Set, Loki, or other deities as manifestations of this one awareness. However, many if not all Theistic Satanists understand that these names ascribed to this one entity are not to be taken literally. Also contrary to common opinion, a true theistic Satanist does not *worship* satan, merely acknowledges that the creator deity, the essence of nature and the universe is all connected to the Current.

In fact, the point of commonality between all minor categories of Satanism is the refusal to humble oneself before a creator deity. To do so is contrary to the basic philosophical principles of Satanism.
Therefore, the Atheist Satanist and the Theistic Satanist should approach Ritual and Magick in the same way, creating little difference in action and expecting the results to be gained in the same way.
The only difference is that the Atheist Satanist would view Satan as a manifestation of their own mind and the culture from which they draw influence, and the Theistic Satanist would view Satan as a primordial awareness, and that they acknowledge it with their own mind drawing reference from the culture around them.

Non-Satanists

Outside of this description Satanism you have those that claim a worship of Satan and a worship of Demons.
These Satan or Devil worshipers are not part of True Satanism as established and are universally considered "Pseudo-Satanists" by valid Satanists.
Some of the traits of a "Pseudo-Satanist" are;

1. Belief that Satan is a literal entity. Literally tempted Jesus, literally fell from Heaven and rules over Hell. Such ideas are the manifestations of Christians, who know very little about world history, culture, religion, philosophy and have decided to reverse the Christianity that they were indoctrinated with as children. Taking up the cause of the "underdog" or "bad guy" and acting accordingly.You will not find a person of Jewish heritage or Hebrew tribal affiliation that is also aware of the religion in which their tribe gave birth, adhere to this philosophy. The main reason is that in Judaism, Satan is actually "part of the God's court." Working with the blessings of God. There is no Rebelious Angel story, this was created along with many other christian myths in the beginnings of the Christian cult.
    
2. Belief that Demons are more than mythological creations and claim communication with them. A pseudo-Satanist or Satan/Devil worshiper will often claim that they influence them or the world around them with the assistance of Demons.Not only is this universally laughed at by legitimate Satanists, it is also considered outside of the main tenet of Satanism in that the individual should and can change their environment with their own will. They understand that they must achieve such change without the need of a supernatural crutch.
    
3. Belief that a pagan deity such as Lucifer, popularly villified by Christian tradition and given the role of the Devil, actually is the Devil. They worship and pray to "Lucifer" seeing this term used interchangebly with "Satan." They also use other deities such as Loki or Pazuzu. While a true Satanist may utilize the mythology and imagery, they draw a very distinct line between their personal use of mythological imagery and worship of the mythology.

Aesthetic

There is no universal Satanic aesthetic. Manner of dress or mode of ritual depends on the individual. There has been common misconceptions, mostly due to the prevelance of a certain Satanic sect, that Satanists have a common look that they prefer to adhere to.
This is simply not true. Satanism and Satanists are not bound with uniforms. As Satanists are found in every walk of Life, so their dress and preference in Music, or Ritual, fall in line with the common culture in which they live, or simply their individual penchant. One may prefer to use Arabic aesthetic in their ritual settings, utilizing Shemaghs, Robes and Arabic language to convey a certain emotional state.
Others prefer to use Middle Age Satanic Aesthetic, using the Black Mass and Christian clothing and imagery.
This is usually in some from of defacement, such as the defacement of the eucharist, etc.
However, especially with former Catholics who have come into the awareness of Satanism, they use Catholic imagery in a similar fashion as those that practice Voodoo. They use Saints, Crucifixes, images of Mary etc. to actually represent Satanic virtues. This is found mostly in individuals that enjoy the art, not out of any reverence for the intent of the images. You will notice that they also find an appreciation for Voodoo myth and imagery. They use Voodoo mythology as any Satanist uses mythology, for their own aims.
Whether it is Kabbalah, Cthulhu, or the ficticious Sith of Star Wars, a Satanist is free to use anything and everything in order to reach their goals. This creates one of the most visually dynamic Philosophies/Religions in the world. There is no common appearance, only common understanding that such visual commonality is non-existent.

Magick/Magic

Satanists might and often practice Magick, in fact some have argued that Satanism without Magick is mere individualism and to remove the occult trappings and study from Satanic life removes the essence of Satanism. Even in the way of wearing a medallion on a regular basis, this becomes a form of ritual, or magick, especially if that medallion is mindfully worn, in honor of your own Satanic nature.

A satanist is not required to practice or study Magick, also spelled Magic by those who are not influenced by Aleister Crowley. Magick, when practiced, is done in a style that is of the choosing of the practicioner. There have been many books written containing Satanic Rituals, but these are mere suggestions. There is no fixed Satanic ceremony. Popular rituals are found in such works as the Satanic Rituals by Anton LaVey. However, even then, many Satanists prefer to use rituals found in Hermetic and secret societies such as The Golden Dawn, or the Ordo Templi Orientis.

You will find that the whole spectrum of Occult Science can and will be tapped into by the Satanists in order for them to achieve their ritual goals. This creates no established way of Magick, but rather and understanding that your way must be discovered on your own.

Satanic Days of Importance

There are no set days of importance for the Satanist, yet there are days which have popularly become connected with Satanism. More accurately said, Satanists commonly celebrated these holidays.
Such days are;

Walpurgisnacht: Celebrated on April 30th or May 1st is the Feast of St.Walpurgis, also known as Witches Night.

Samhain/Halloween: Celebrated on October 31st is linked with Celtic Pagan customs for observances for the dead and assumed the Celtic new year, however Scholars have found that this claim is not true.

Dia De Los Muertos: The Day of the Dead, celebrated on November 1st and 2nd.

The Seasonal Solstices:

-Winter Solstice which will occur;

December 21 in 2008, 2009, 2010, 2012, 2013, 2014.
December 22nd in 2007, 2011

-Summer Solstice which will occur;

June 20th in 2008, 2009, 2010, 2011, 2012, 2013, 2014.
June 21st in 2007

The Seasonal Equinoxes:

-Spring Equinox which will occur;

March 20th in 2008 through 2014
March 21st in 2007

-Autumn Equinox which will occur;

Sept. 22nd in 2008, 2009, 2012, 2013
Sept. 23rd in 2007, 2010, 2011, 2014

Your Birthday, or the Birthday of a loved one.

Other minor celebrated holidays are the Birthdays of Anton LaVey (April 11th) and Aleister crowley (October 12th)