Reference Book: Star Wars Saga Edition Jedi Academy Training Manual
See also: Philosophy
Those who walk the path toward The Dark Side of The Force go through four different stages: Temptation, Imperilment, Submission, and Atonement or Redemption. Most users of The Force, even the purest of The Jedi, can go through at least one of these stages as they walk through life. Those who are ambitious, power-hungry, filled with hatred, overly passionate, or just outright evil will experience two or more of these stages during their descent into darkness. Anakin Skywalker went through all four stages during his life: Temptation as a Jedi Padawan, Imperilment while he served as a Jedi Knight during the Clone Wars, Submission when he served Darth Sidious as his apprentice Darth Vader, and Redemption when he hurled Sidious to his death and restored freedom and order to the galaxy.
Force-users can face these stages in a variety of different ways. Pupils and apprentices can grope with these stages as they learn about The Force, their sense of morality, or their affinity with The Jedi Code.
To those who can feel it, The Force offers great power. An individual sensitive to The Force views the galaxy in a much different way than those who cannot connect to The Force. Through that insight, one can learn to use The Force in many ways but also runs the risk of having a brush with The Dark Side.
As a Jedi begins to learn to wield The Force and master its techniques, they open themselves to the Temptations that come with it. Those who show impatience or eagerness to engage in combat are especially susceptible to The Dark Side's lure, as they quickly take an aggressive stance and often give in to fear or anger. If this course of action is what the Jedi prefers, then they should expect The Dark Side to tempt them in some way.
A Force-user who has been tempted by The Dark Side enough to be on the verge of completely falling under its influence is considered Imperiled, and great strength of will is required to pull them back from the edge of the abyss on which they stand. While some show little concern about taking that last step to becoming a full Dark Sider, others resist The Dark Side's call and try to use its power sparingly. They hear the voice inside their head warning them to not perform an act that will push them over the edge. Sometimes that voice is a whisper; other times it roars like thunder.
Once a Jedi has completely submitted to The Dark Side (That is, once their Dark Side Score equals their Wisdom score), all bets are off. They no longer has any need, let alone desire, to monitor their actions, for they have become a full-fledged Dark Sider whose agenda has totally changed from what it was at the beginning of their descent. Those who once worked with them now see what they have become and might choose to take appropriate action, including trying to kill them. More than likely, the Dark Sider will leave the group to pursue their own goals and never see them again except as an adversary.
Atonement or Redemption Edit
Most of the time, one who is steeped in The Dark Side has no desire to return to the life they once led, wishing instead to continue along The Dark Path. However, exceptions exist. Those who are tainted might atone for their actions and are able to go through the effort to Redeem themselves. Those who have fully Submitted to The Dark Side cannot Atone and can only be Redeemed through an act of Dramatic Heroism.