I should give fair warning before diving into this outline: I'm not going to teach you the basics of roleplay; I'm going to hope that you already know that or that you've hopped over to Storyboard a few times. Secondly, I will use terms like "proper" or "best." Understand that I use those words from my perspective and that other players have a different and equally legitimate perspective, too. Lastly, this is far from exhaustive, and if you have any questions, I will spend some time in the comments answering them, or you can feel free to hit me up on Twitter.
The first major hurdle when playing a Sith is understanding the Imperial culture. If you are going to play a character who lives in the Sith Empire, you have to remember that the Empire does not function in any way like the United States or any other country in the western world. In fact, I would be hard-pressed to find any active country on Earth that functions exactly the same way the Empire does. The best description for the Empire is a totalitarian theocracy, although to call it a theocracy might be a stretch because the Emperor is not exactly a god. And although the Force is very real, Sith philosophy is religious, and the citizens of the Empire understand and subjugate themselves to those who wield its power.
I'll dive into the religious aspects another time, but I would like to give you a clear understanding of where each Sith fits into the social structure. Although many people would like to believe that their Sith falls outside this social structure so are therefore more powerful, it's simply untrue. The Sith work best when unified in an unbreakable chain. Each Sith is subject to another Sith unless he is the Emperor. Now, I'm not saying that in order to play a Sith you have to have a player who is your master, or frankly, that you have a master at all. But it would behoove you to attempt to fit into the social structure somehow.
At the very top of the list is the Emperor. He is a canon character, and no respectable roleplayer would ever claim to be him. Other untouchable characters are the Dark Council members. Yes, I know that one of the storylines allows you to become a Dark Council member, but I would suggest not taking that story as your character's canon.
That Dark Council member's name is Darth Nox; he leads the Sphere of Ancient Knowledge. Each Council member heads up one of these Spheres, and there are 12 in all. And if you are looking to get into Sith roleplay, this is a good place to start. Ask yourself what is important to your character. Is he a warrior? Then maybe he should be a part of the Sphere of Defense. Is she an archaeologist? Then maybe the Sphere of Ancient Knowledge is for her. I have a Sith who is a businesswoman. Making money for herself and the Empire is most important to her. Sure, she uses the Force and can call on it to defend herself if needed, but she is more likely to try to outmaneuver her opponents politically or financially before trying to face them head-on. She serves the Sphere of Logistics headed up by Darth Vowrawn.
After determining which Sphere your Sith belongs to, think about where he fits in the political structure.
All Dark Council members carry the title Darth, as do the Sith directly under them. In fact, it's possible that multiple levels within the hierarchy can contain members with the title Darth, although I'd venture to say that most of the time you wouldn't find more than a couple of tiers of Darths. Darths have earned their titles by some sort of extraordinary act that gained notice of the Dark Council or someone high up in the Sphere with influence in the Dark Council. If you want to be a Darth, be prepared to tell the story of how you became a Darth. Personally, I don't recommend your taking the Darth title unless you have a group of people who are willing to follow you or accept that you hold that title.
If you don't want to have to come up with that story, or if you're not looking for the power struggle that happens at the Darth level, then maybe you should consider making your character a Lord. Lords usually work directly under a Darth or directly for a Sphere if circumstances have caused their master to no longer be around. Lords are indirectly subject to anyone who is a Darth, but they always answer directly to someone. If you're looking to be independent... well, I talked about that earlier. You might not have complete freedom as a Lord, but you are very free to jump from Darth to Darth if your story demands it. A Darth's career is pretty much set, but a Lord can feel free to change careers midstream.
Acolytes and Apprentices are similar in where they fall in the social order. Both are subject to all other Sith, and given the right circumstances, they might also be subject to some Imperial military personnel, like Admirals, Generals, or Moffs. Acolytes are Apprentices without a master, but otherwise they hold the same position in the hierarchy. If you're considering playing an Apprentice or Acolyte, which can be good for new players, understand that you are the lowest on the totem pole, as it were. Mouthing off to those who outrank you has consequences, so be prepared to deal with that if you decide to take this path.
Unfortunately, I have not been able to dive into religious or personality aspects of playing a Sith, so I will have to do that in a later Hyperspace Beacon. However, I hope this is a good start, and if you have any questions, feel free to ask. I will see you in a galaxy far, far away.
The Hyperspace Beacon by Larry Everett is your weekly guide to the vast galaxy of Star Wars: The Old Republic, currently in production by BioWare. If you have comments or suggestions for the column, send a transmission to firstname.lastname@example.org. Now strap yourself in, kid -- we gotta make the jump to hyperspace!