I just started shooting film again today (whee!) after a 10-year hiatus and I thought it was important to remind myself what all the simple tricks of film photography were. The Art of Photography explains here what pushing and pulling film does and it was a good refresher for somebody like me who once learned the concept but has kind of forgotten it over the years while shooting digital.
I remember learning about this at Parsons and developing quite a few number of rolls of film that were pushed to a higher speed to get a bit more contrast. I never did it with color film though. Might do that with some really expired film I have just to see.