Now, some of you may know me from the EvocationMagic forums, where this was originally posted. I've posted there under the handle "Wanderer" since the end of 2009, and recently a thread was started about Satan. That being the case, I added my commentary in the thread, and its proven to be very helpful to some practitioners. If you're interested in reading the information therein, click here.
That said, to rehash what I wrote therein, Satan, as we understand Him, is a very misunderstood being that was mentioned, albeit breifly, in the Bible. When He does show up, its in the context of Him being an accuser or an opposer, and that's actually fairly apt. Unfortunately, with the advent of Christianity and the obsession of the Good vs Evil dichotomy, we've largely lost sight of the function such an entity plays. In Hinduism and Buddhism we oft see entities like Amithaba or Kala Bhairava that play a similar role, and They are recognized as being wrathful manifestations of Gods of compassion who are there to force us to grow. Satan plays the same role, though from a Western point of view.
Having said as much, the function and use of such a spirit really is rather obvious; He's, in many ways, a necessary "evil", as stagnancy is toxic to us. It keeps us complacent and allows progress to elude our grasp. If you feel as though life has proven to be much too stagnant for your liking, I would heartily suggest that you conjure Him and ask for help in cutting through the obstacles that keep you bound to your current situation.
Above, I've included the picture of His sigil. In this endeavor, I leave it to you to come up with your own rituals. As always, proceed cautiously, as the consequences and responsibilities fall to you. If you do undertake this work, please be sure to share your results.