Why is my Surly Long Haul Trucker touring bicycle's chain jumping?

When I'm riding my Surly Long Haul Trucker bike, the chain keeps jumping around--I can't tell what the problem is, or how to fix it. It does this even when I don't change gears.Why is my Surly Long Haul Trucker touring bicycle's chain jumping?
It can be just a simple barrel adjustment on the rear derailleur. Watch this video and don't touch the screws.



http://bicycletutor.com/adjust-rear-dera



Make sure you are not cross chaining.



http://bicycletutor.com/gear-shifting/Why is my Surly Long Haul Trucker touring bicycle's chain jumping?
If you have changed the rear cassette and did not replace the chain, it will skip. It could also be out of alignment. There is a barrel screw where the cable goes into the rear derailleur. It adjusts the derailleur to the cassette laterally. It may need to be adjusted. If you've had an accident lately, it could be that your derailleur hanger is out of whack. Prolly nothing to do with chain tension. That's all I can think of right now.