Please Note this is not my guide I found this on the swtor community forums : http://www.swtor.com/community/showthread.php?t=157437
First, some background. Nearly every stat in the game follows a diminishing returns curve. For those mathematically-oriented, these curves asymptotically approach a certain limiting value.
For those not so mathematically inclined, that basically means that the benefit you gain from adding a certain amount more of that stat gets smaller and smaller the more of it you have, with a certain "ceiling" it can never exceed. For example, crit rating limits to 30%. Thus the more and more crit rating you add to your character, the closer and closer you get to that 30% bonus, but you can never actually reach it.
Also, note that the benefit from each stat is on a separate DR curve, and raw percentage benefits (such as from abilities) have no effect on any DR curves (they are additive on top of them instead). Thus how much Willpower you have, for example, has no bearing on how much benefit you get from X crit rating, and vice versa. This doesn't imply that the DPS value of the stats are independent, but that's another discussion entirely.
Willpower
Increases force damage, healing, and critical effect chance. Each points provides 0.20 Force Bonus Damage and 0.14 Force Bonus Healing. Critical effect chance benefit scales slowly and limits to 30%.
Force Power
Increases force damage and healing at a slightly higher rate than Willpower. Each point provides 0.23 Force Bonus Damage and 0.17 Force Bonus Healing.
Power
Identical to Force Power for Sorcerers. Each point provides 0.23 Force Bonus Damage and 0.17 Force Bonus Healing. Also increases melee, ranged, and tech at the same rate.
Critical Rating
Increases critical effect chance with all damage and healing abilities. Benefit scales moderately and limits to 30%.
Surge Rating
Increases the bonus damage or healing from a critical effect. Additive with the base 50% critical multiplier. Benefit scales rapidly and limits to 50%.
Alacrity Rating
Reduces the cast time of casted and channeled abilities. Additionally reduces the length of the global cooldown for those ability if their cast or channel time drops below 1.5 seconds. Does not reduce the GCD for instant abilities, nor for cast/channeled ones if their final cast time remains above 1.5 seconds. Additive with multiple Alacrity sources. New Cast Time = Original Cast Time * (1 - Alacrity%). Scales moderately and limits to 30%
Accuracy Rating
Reduces chance to miss against a target, and once miss chance is 0%, begins to negate the target's Defense or Resistance. Boss targets are believed at this time to have zero innate resistance, and force attacks have a base accuracy of 100% against all targets. Thus, this stat is worthless for Sorcerers in PvE. In PvP, no gear stat gives resistance, and only limited abilities do, generally short duration defensive cooldowns. Thus it is generally worthless against most targets. Scales moderately and limits to 30%.
Shield Rating
Increases your chances of "blocking" and attack with your shield generator. Referred to as Glance Rating on TORhead. Requires a shield generator in offhand, and thus is useless to Sorcerers. Scales moderately quickly and limits to 50%.
Absorption Rating
Increases the damage absorbed by a successful shield "block". Does not increase the damage absorbed by Static Barrier or similar absorption buffs/abilities. Requires a shield generator in offhand, and thus is useless to Sorcerers. Scales rapidly and limits to 50%.
Defense Rating
Increases your chance to avoid melee and ranged attacks. Dodge, parry, and a few other terms are all manifestations of this stat. Sorcerer base defense is 10%. Has no effect on Force or Tech attacks. Generally useless to Sorcerers. Scales moderately and limits to 30%.
Expertise Rating
PvP-only stat. Increases your damage and healing done to other players and decreases the damage you take from other players (all 3 at the same rate). Healing is increased by "ignoring" part of the Trauma buff that is automatically applied when you enter PvP combat, and thus scales somewhat better in actual effect than the damage or DR bonus (though it will display the same on your character sheet). Scales moderately slowly and limits to 20%.
First, some background. Nearly every stat in the game follows a diminishing returns curve. For those mathematically-oriented, these curves asymptotically approach a certain limiting value.
For those not so mathematically inclined, that basically means that the benefit you gain from adding a certain amount more of that stat gets smaller and smaller the more of it you have, with a certain "ceiling" it can never exceed. For example, crit rating limits to 30%. Thus the more and more crit rating you add to your character, the closer and closer you get to that 30% bonus, but you can never actually reach it.
Also, note that the benefit from each stat is on a separate DR curve, and raw percentage benefits (such as from abilities) have no effect on any DR curves (they are additive on top of them instead). Thus how much Willpower you have, for example, has no bearing on how much benefit you get from X crit rating, and vice versa. This doesn't imply that the DPS value of the stats are independent, but that's another discussion entirely.
Willpower
Increases force damage, healing, and critical effect chance. Each points provides 0.20 Force Bonus Damage and 0.14 Force Bonus Healing. Critical effect chance benefit scales slowly and limits to 30%.
Force Power
Increases force damage and healing at a slightly higher rate than Willpower. Each point provides 0.23 Force Bonus Damage and 0.17 Force Bonus Healing.
Power
Identical to Force Power for Sorcerers. Each point provides 0.23 Force Bonus Damage and 0.17 Force Bonus Healing. Also increases melee, ranged, and tech at the same rate.
Critical Rating
Increases critical effect chance with all damage and healing abilities. Benefit scales moderately and limits to 30%.
Surge Rating
Increases the bonus damage or healing from a critical effect. Additive with the base 50% critical multiplier. Benefit scales rapidly and limits to 50%.
Alacrity Rating
Reduces the cast time of casted and channeled abilities. Additionally reduces the length of the global cooldown for those ability if their cast or channel time drops below 1.5 seconds. Does not reduce the GCD for instant abilities, nor for cast/channeled ones if their final cast time remains above 1.5 seconds. Additive with multiple Alacrity sources. New Cast Time = Original Cast Time * (1 - Alacrity%). Scales moderately and limits to 30%
Accuracy Rating
Reduces chance to miss against a target, and once miss chance is 0%, begins to negate the target's Defense or Resistance. Boss targets are believed at this time to have zero innate resistance, and force attacks have a base accuracy of 100% against all targets. Thus, this stat is worthless for Sorcerers in PvE. In PvP, no gear stat gives resistance, and only limited abilities do, generally short duration defensive cooldowns. Thus it is generally worthless against most targets. Scales moderately and limits to 30%.
Shield Rating
Increases your chances of "blocking" and attack with your shield generator. Referred to as Glance Rating on TORhead. Requires a shield generator in offhand, and thus is useless to Sorcerers. Scales moderately quickly and limits to 50%.
Absorption Rating
Increases the damage absorbed by a successful shield "block". Does not increase the damage absorbed by Static Barrier or similar absorption buffs/abilities. Requires a shield generator in offhand, and thus is useless to Sorcerers. Scales rapidly and limits to 50%.
Defense Rating
Increases your chance to avoid melee and ranged attacks. Dodge, parry, and a few other terms are all manifestations of this stat. Sorcerer base defense is 10%. Has no effect on Force or Tech attacks. Generally useless to Sorcerers. Scales moderately and limits to 30%.
Expertise Rating
PvP-only stat. Increases your damage and healing done to other players and decreases the damage you take from other players (all 3 at the same rate). Healing is increased by "ignoring" part of the Trauma buff that is automatically applied when you enter PvP combat, and thus scales somewhat better in actual effect than the damage or DR bonus (though it will display the same on your character sheet). Scales moderately slowly and limits to 20%.