I found this short video below that gives some good insight on how the center should block (or at least his thought process) when the left guard is pulling (left to right).
I personally always thought the center is the most important position on the offensive line. This is not only your ignition point, but usually your communicator to the other linemen in regards to fronts, blitz looks, etc...
How an Offensive Line Center Does a Choke Block -- powered by eHow.com
Keep spreading e'm!