In this video, YouTube user Beausafk shows us some tips on farming Eridium in Borderlands 2. Specifically, farming Eridiuim in the town of Sanctuary.
If you're not familiar with the substance, Eridium is a brand new element found in Borderlands 2. Eridium can be absorbed by Sirens (although not all of them, as Maya cannot do this) to enhance their powers and make them even more formidable.
In Borderlands 2, Eridium can be stocked up and used as a form of underground currency to purchase character upgrades on the Black Market. The substance is very rare, but Beau makes it a little easier in this guide.
The element is very rare, so don't get disappointed if this method only yields a few bars of the stuff. Some is better than none, and you can always repeat the process for more Eridium.