Item modification in SW:TOR can be a little confusing and different for some players. However it is similar to using 35pt powerbits in SWG, enchanting in WOW, or adding runes in Rift.
Keep in mind as your progress through the game that any item that has modification slots can be upgraded. Armor and Weapons can have different slot types and not all armor/weapons have every available modification slot. Higher level items also may have more slots then lower level items and thus can potentially hold more modifications.
Since TOR will not have a wardrobe function in place at launch It is advised that you hold on to any items that you like the look of cosmetically. You can then add higher and higher level modifications to it to theoretically continue using it right up to max level.
Mods can be removed from an item for a nominal fee that scales with the item level via ctrl+right clicking the item and then dragging the mod into your inventory. Mods can also be overwritten by dragging and dropping another mod into that slot without first removing it.
Modification Types as of the time of this post are as follows:
- Enhancements: Used on weapons and armor, fairly common and increases various stats depending on the enhancement type (strength, endurance, aim etc.)
- Mods: Used on both weapons and armor, same as enhancements add stat based increases and can contain more then 1 stat.
- Armor: Used on Armor only, this modification will determine the armor value of the item it is placed in. Will also include stat increasing values.
- Hilt: Used only in lightsabers and melee weapons. This mod determines the damage range for the weapon it is placed in. Will also include stat increasing values.
- Barrels: Used only in ranged weapons (pistols, rifles etc), this modification will determine the damage range for the weapon. Will also include a stat increasing value.
- Color Crystals: Used in all weapon types, the color of the crystal determines the color of the saber, melee blade, or the energy beams from ranged weapons. Can sometimes have stat increasing values on them as well.
Where to Obtain Modification items:
Item mods can be found via loot, quest rewards, and even crafting. Several of the crew skills make some form of item modifications and can even discover rarer schematics via reverse engineering. You can also keep an eye on the Galactic Trade Network for both unassigned modification items and for armor/weapons that contain mods. You can then purchase these, rip them out of the item and put them in your own gear.
The above guide also goes for your companions and their gear, so keep an eye out for upgrades for them as well as yourself.