This method allows you to easily stack Nephalem Valor and get some rares from Inferno Act 2 elites and Zoltan Kulle. It probably works only for ranged classes, I do it with Wizard.
1. Select The Black Soulstone - Soulstone Chamber quest.
2. Take a waypoint to Desolace sands.
3. Find and enter the Vault of the Assassin. It might take some time and deaths.
4. Now the most important trick is to kite elites inside the Vault of the Assassin to this spot:
The room might look different you can just leave game and resume until you get the right layout. After you get them there just die. Resurrect and now you can easily kill them like this:
The Vault usually has 6-7 elites so you can stack your Nephalem Valor and get quite a few rare items.
5. After you are finished you may kill Zoltun Kulle with 5 stacks of Nephalem Valor. The boss is pretty easy so I will not describe in detail how to kill him.
Alternatively instead of Zoltun Kulle you can go for Belial if you can kill him of course.
A few more tips. This method allows you to kill elites while wearing your Magic Find. Also try to stay as far away as possible while killing Mortar or Teleporter mobs.