From the Guard Antonio Nogueira demonstrates a nice double arm bar set up in the video above.
Basically he starts with head & arm control from the guard but he adds the detail of driving his forearm into his opponent's collar bone. This will make the head & arm clinch tighter and help to lock your opponent in place.
Next he escapes his hips at an angle off to the side as he passes his opponent's arm passed his head and gets to his side.
At this point his opponent tries to square back up. He then closes a high guard over their shoulder which leaves their arms wide open for the arm bar.
