This is an article from Helium written by Matt Bird. It is more applicable to D&D 3.0/3.5 and Pathfinder RPG than the current version of D&D.

Your typical Dungeons and Dragons PC will run the gamut from lawful good to chaotic neutral. Most bands are composed of a mixture of good to legally-ambiguous guys and gals who want to put an end to evil in the world. These groups are probably the easiest to handle and participate in, for though the methods may be different the ends are usually the same.

But that narrow view of Dungeons and Dragons eliminates three alignments: neutral evil, lawful evil and chaotic evil. These simple choices can dramatically change how a character acts.

At its basic an evil character is easy enough to understand. They're the bad guys. They work to make everyone else miserable, thinking only of their own goals and ambitions. And, typically, they don't wind up in a group of good guys. Evil characters are on the other end of the sword. Or they would be in a black and white game. Dungeons and Dragons is seldom black and white. There are plenty of morally-ambiguous situations in which good and evil can come together to complete a common goal. And though they don't always get along together - indeed the union may result in eventual disaster - it's perfectly reasonable to expect a group with good and evil characters to eventually succeed.

That is, so long as the PCs don't act TOO evil.

Playing an evil character who's true to their nature will require some evil acts. Villains have little by way of scruples and will cheat, lie and kill to get what they want. This usually contrasts with the beliefs of good characters who, understandably, loathe harming the innocent (and even those who aren't so innocent, or at least not for a good reason).

But that doesn't mean you need to be overtly evil all the time. Think about villains in real life (or people you perceive to be villains, anyway). Do they constantly wander around killing people in the streets? Is their every last act tempered by malice? Or can they hide their temperament when they realize it's a dumb idea to be evil? Likely the latter, if they want to remain free.

And you should act similarly if you want to play an evil character. By all means, kill people if you're evil. Steal. Cheat. Lie. Slander. But don't parade around committing evil acts all the time. Don't get your party in trouble just because you're 'playing in character'. In short, don't be an idiot about being evil. Be sly, be opportunistic and, above all, be discrete. Carrying out vile acts behind the backs of your allies will ultimately be more fun than turning into a ravenous axe murderer, especially if you want to survive more than one session.

One last practical tip: if you want to go evil, you may want to avoid chaotic evil. Chaotic evil characters tend to act on their impulses on a whim, doing as they please when they please. There's a reason most monsters are chaotic evil. Go with neutral or lawful evil and you can create a much more sociable, balanced character who can interact with goody-goodies while remaining true to your vile nature.

Have you heard of TORG? The classic game from the 1990s. Would you play in a TORG game if you had access to the rules? Have you ever played TORG before? Do you like multi-genre settings? Torg is a cinematic multi-genre role-playing game (RPG) created by Greg Gorden and Bill Slavicsek and released by West End Games in 1990, which uses several innovative techniques. Players take the role of Storm Knights, deliberately larger-than-life heroes engaged in fighting the invasion of Earth, to prevent it being conquered by several invading dimensions (called cosms), each with its own separate reality; cosms largely correspond with popular role-playing genres.

Notable features

* Deriving enjoyment from how characters, equipment, and environments of the various realities interact, such as having Terminator-style futuristic cyborgs adventure alongside Dungeons & Dragons-style mages in an Indiana Jones-style pulp setting.

* Playing a game with an explicitly epic or 'cinematic' overtone (as in Star Wars or Buffy the Vampire Slayer, as opposed to RPGs like Vampire: The Masquerade or Dungeons & Dragons).

* A unified mechanics system suitable for any setting; character attributes and game mechanics use a single sliding scale ('18' can equally mean an hour of time, a truckload of weight, an expert markman's skill, or $4,000) and a unified method of task resolution involving a d20.

* The game's backstory involves 'possibility energy', which can be used by Storm Knights to achieve heroic feats. In the game mechanics a spent possibility gives a player a chance to make an additional die roll, potentially leading to greater success. Similarly, an included deck of cards provides bonus rolls or skill points and contains ideas for additional character interaction. Some of these cards can be used instead of Possibility energy.

* An open-ended die mechanic: one twenty-sided die roll, read through a bonus chart, gives the bonus to a character's skill for that attempt. Barring special circumstances, the die may be rolled again (and the subsequent total added to the first roll) each time a 10 or a 20 is rolled. Along with re-rolls gained through spent possibilities, card play, and other possible influences, this allows truly spectacular feats to be accomplished by player characters.

* Emphasis on groupwork and character interaction by exchange and giving of cards, coordination rules, and the use of "group powers."