Multiple World Record holder and Powerlifting legend, Steve Goggins demonstrates the correct way to perform pin pulls.  Start at the 1:22 mark until the 2:45 mark to see Steve work up to 1000lbs.  One unique aspect of Steve's pulling technique is the how he leans back and keeps his shoulders behind the bar initially and then drives the hips through to finish.  This seems to have a better correlation to completing the top portion of the deadlift.

This particular training session included:

Deadlift: 445x1, 545x1, 660x1, 760x1,

Rack pulls, 660x3, 750x1, 840x1, 930x1, 1000x1, 840x5

Shrugs 450x8, 660x8