From the main menu, select System and open the Character Configuration menu, then select the Display Name Settings tab from the column on the left. Under General, check the box labeled "Display class or job icons with nameplate." and choose your preferred icon type.

With these icons enabled, you can easily view the classes and jobs of your adventuring companions without having to check your party or alliance list in the midst of battle.

* Class/job icons may not display during certain PvP modes.
* When class/job icons are enabled, the online status above a player may display at a smaller size, or not display at all.