Identifying and Unidentifying
Identifying and unidentifying is a very simple process, however be aware that randomly generating attributes for your gear can get expensive, since it is random. It is suggested to only start doing so at level 50+.
The Process
Identifying an item will generate random attributes, some will come into effect straight away while the other attributes will only be reached by enchanting the item. Depending on the type of gear you can get either 1 or 2 additional basic attributes. This means you will feel the effect of those attributes even if you do not strengthen the item. You can only generate the same attribute twice; once as an immediate attribute and again as an attribute which is unlocked via enchanting. The only way to get three of the same attribute on you gear is if the attribute is already present as a base stat and you generate two more of the same attribute on top of that.
After an item has been identified it can be unidentified if you wish to generate better attributes which are more specific to your class. To generate attributes which satisfies your requirements you can just keep identifying and unidentifying your gear. This process can become quite expensive and is therefore only recommended once you reach level 50+.
In the post above I explained which attributes you may want to focus on getting depending on your class, make sure you have read it. Once you are satisfied with the attributes, or are just tired of trying to get the perfect stats, you will use the enchanting system.
Gear classification differences
Depending on the type of gear you are using the random attributes will be generated at different enhancement steps:
PvE Gear = +3/+6/+9
Crafted Gear = +3/+5/+7/+9
PvP Gear = +1/+3/+5/+7/+9
As you can see, crafted gear does gain an extra attribute over PvE gear. This is why crafting gear can be a good alternative when leveling up. However at high level it is less viable for various reason (mainly it is very expensive to craft armour that compares to the good drops).