Route 1
You can begin by stacking getting some Nephalem Valor stacks in the Black Canyon Mines or Desolate Sands, but this is not necessary. Both of these zones are fairly mediocre, but they are easily accessible and work well enough to gain a couple stacks of NV.
The run starts in the Dahlgur Oasis. This zone is not slightly worse than Desolate Sands and Black Canyon Mines in terms of Mob Density, but it connects to the Ancient Waterway which houses two of the best farming Maps currently in the game. Simply Clear through the Dahlgur Oasis until you find the Ancient Waterway, don't worry about clearing the entire zone.
You may run into the Forgotten Ruins while clearing out Dahlgur Oasis. Clear this dungeon as it is very easy and has excellent mob density.
Once you reach the Ancient Waterway, head inside. This is where the run truly starts.
There will be three entrances to different maps within the Ancient Waterway. Begin by taking the Western Channel entrance. This zone is full of massive packs of very easy monsters, primarily Skeletons. The map is fairly linear and you will have almost no problem finding your way around. Keep clearing until you reach the Western Flow Control.
The Western Flow Control leads to an empty balcony area which houses the entrance to the Eastern Channel.
Head into the Eastern Channel and clear through the entire map. It is similar to the Western Channel with huge packs of very easy enemies, but there tends to be groups of Construct monsters which can deal a large amount of damage if you are not careful. Once you reach the Eastern Flow Control the run is finished.
From here you can either remake the game, kill the Keywarden in Dahlgur Oasis with your 5 stacks of Nephalem Valor (if you haven't already), or continue on to Run 2.
Route 2
You can either continue from Run 1 or Start in the Desolate Sands or Black Canyon Mines to stack Nephalem Valor.
I prefer to just jump right into the Archives of Zoltun Kulle and get to farming..
Upon entering the Waypoint, cross the small bridge ahead of you. From there you will see a large portal in the center which takes you to the Zoltun Kulle fight and three smaller portals connecting to different maps. You will be clearing each of these smaller portals.
The Storm Halls is the best map available in this run. It is full of large packs of skeletons with some Imp packs as well, both of which are extremely easy. You will occasionally run into other Monster types, but only constructs will be a threat. After clearing this zone just teleport out and take the Archives of Zoltun Kulle waypoint again.
The Unknown Depths is next, this zone has a little less mob density than The Storm Halls with similar monster types. It's still one of the best maps in Act 2 for overall kill speed.
The Realm of Shadows is last, this zone was nerfed pretty heavily during beta. This used to be by far the best zone to farm in, but now it's merely mediocre. It's still incredibly easy and you may as well clear it while you're here.
You can finish the run off by killing Zoltun Kulle or simply remaking the game.
