WoWDB

To track how many enemy players you need to kill in each sub-zone:  Add the achievement to the Objectives tracker.  (Open the Achievements window.  In the left column: click Player vs Player, click Wintergrasp.  Go to the larger, right column and scroll if needed down to "Wintergrasp Ranger."  Checkmark the Track box or Shift+Leftclick.)

This achievement was much, much easier to earn in Wrath of the Lich King when the world PvP zone was current content.  Nowadays, you may have to resort to finding an opponent willing to allow you to kill him or her.*  Thanks, Yin!

*  Recently Slain does not interfere with credit towards Wintergrasp Veteran.