WoWDB

The best place to farm rep for this faction is Socrethar's Rise in Shadowmoon Valley.

Just make sure you don't do it when it is the daily, or the area will be packed.

A letter is mailed to you when you reach Revered with this faction:

From: Exarch Akama
Subject: The Exarchs have Faith in You

<Player>,
  You have proven yourself to be a great friend to the Council of Exarchs, an indispensable ally in our time of greatest need. Thank you for your continued efforts to defend Auchindoun and reclaim Shattrath. The Prophet once told me that we only see shadows before us when the light is at our back. With faith, we will prevail!
  I have spoken with Vindicator Nuurem, the Exarch quartermaster located at the Stormshield town hall in Ashran. Some supplies are available to you there.
  - Exarch Akama
  High Vindicator of the Exarch Council