From lvl 1 - 15 must follow these:

if ur f2p:

    *  Do quests and fight mobs in Incarnam. (You can also go to Astrub and do your class
quest to be booted to level 3.)
    * From lvl 7-8 Incarnam Dungeon can be a good place for xp.
    * Another good place are the Gobballs up to level 10
    * Lone Plants (Demonic Roses etc.)
    * Some quests in Astrub can be an alternate source for XP
    * At level 15, you can choose to continue training in Incarnam (eg. fighting
Prepubescent Chafers or Sick Grossewer Milirats) or move on to Astrub.
    * Around level 12, Boars and Prespics are also good. 

if ur p2p:

    *  From approximately level 10, you may choose to leave Incarnam  for the Astrub Rocky
Inlet (where the sand dungeon is)
    * The Blop Prairie is great for experience as well. (Find single Biblops/Blops of an
element that is weak to you). 

MORE CLASSES TO GO....