Everyone seems to think that the most efficient way to creep as Mordor is to use Easterlings, but there is another method that's very interesting.
You are able to creep with three Orc units, which are very effective at it. What about the Warg's trample you may ask? Well, Orc's take very little from Warg creep trample, and so it takes a long time for them to die because of it. Also, there are so many Orcs that even if the Warg's had bitten them all, the creep would still be down first.
Another advantage to this method is you can lead the Wargs to your enemy afterwards.
It can be done following these steps:
Build three hordes of Orcs
Send them to the creep you'd like to kill
Move them around the Warg lair so they'll be attacking from every angle
Have the Orcs attacking the lair in aggressive stance and the Orc that's getting the brunt of the Warg tramples in defensive.
Once the lair has been destroyed, take the cash.
Lead the left over Wargs to the enemy.
This video shows how Orc creeping is done correctly.
Thanks to Aberrance for providing this weeks tip and video!