Here is what I posted in the other thread -
Sith Warrior/Jedi Knight lightsaber forms:
Shii-Cho Form - Enter a balanced lightsaber form, increasing all damage dealt and reducing all damage received by 3%.
This is the base stance all Sith Warriors/Jedi Knights start with.
Ataru Form - Enters an acrobatic lightsaber form. Saber attacks will trigger an extra attack against a second enemy in melee range for 1 damage every 1.5 seconds. Also increases movement speed by 15%, and reduces the cooldown of Force Charge by 5 seconds. Benefits from dual wield.
This is the base Marauder/Sentinel AC DPS stance.
Juyo Form - Enters an aggressive lightsaber form, causing your melee attacks to increase all damage dealt by 2% for 15 seconds. Stacks up to 5 times. This effect cannot occur more than once every 1.5 seconds.
This is an additional Marauder/Sentinel AC DPS stance.
Soresu Form - Enters a defensive lightsaber form, reducing all damage taken by 6%, increasing armor rating by 60% and increasing threat generation by 50%. Soresu Form also increases shield chance by 20%. While active, taking damage builds 1 rage, but all Assault abilities generate 1 less rage. This effect cannot occur more than once every 6 seconds.
This is the Juggernaut/Guardian AC tanking stance.
Shien Form - Enters an aggressive lightsaber form, increasing all damage dealt by 6%. All attacks that cost rage will refund 1 rage when used. In addition, you generate 1 rage when attacked, but this effect cannot occur more than once every 6 seconds.
This is a Juggernaut/Guardian AC DPS stance that has to be spec'd into via the appropriate DPS tree.
Bounty Hunter/Trooper gas/ammo types:
Combustible Gas Cylinder/Plasma Cell - Loads your blaster with combustible gas, giving all of your blaster attacks a 10% chance to deal [?] additional elemental damage over 6 seconds.
The base DOT DPS stance for BHs/Troopers. The bonus damage improves with increased levels of the talent.
High Velocity Gas Cylinder/Armor Piercing Cell - Loads your blaster with a high velocity gas cylinder. While active, armor penetration is increased by 35%.
The burst DPS stance for BHs/Troopers.
Ion Gas Cylinder/Ion Cell - Loads your blaster with ion-charged gas, giving ranged attacks a chance to deal [?] additional energy damage. While this cylinder is active threat generated is increased by 50%. Increases armor by 60%, decreases all damage taken by 5% and increases shield chance by 20%.
This is the tanking stance for Powertech/Vanguard ACs.
High Energy Gas Cylinder/High Energy Cell - Loads your blaster with a high-energy gas cylinder. While active, all internal and elemental damage dealt is increased by 5%.
This is the DPS stance for Powertech/Vanguard ACs.
Combat Support Cylinder/Combat Support Cell - While active, Rapid Shots charges your powercell with each use. Charges increase all damage and healing dealt, up to a maximum of 3% at 30 charges. In addition, targeting an ally with Rapid Shots will heal the target for 100% of your tech bonus healing.
This is the healing stance for the Mercenary/Commando ACs.
Basically for these classes you would pick a stance and go with it pretty much. The exception might be a hybrid Mercenary/Commando that is switching between healing and DPS, but generally you spec into a tree that only takes advantage of a single stance and ties it to your main abilities, so switching stances would be detrimental (in some cases extremely so). The choice is really made for you when you select your particular tree of interest in your AC.
Additionally, Assassins/Shadows can switch between stealth and combat "stances", although I wouldn't really consider them stances as such.