Wish I looked into this a bit more before I gave birth. I remember not feeling much like pushing but with the mw's encouragement, and her praising me everytime I did so, together with all the film images flashing through my mind of everyone screaming "PUSH", and what with the panic, I pushed harder than I think I should have done and remember the moment when I ripped, thinking, that's because I pushed too hard.
The other thing that seems to get a lot of emphasis - by mw's and in films, is to breathe deeply. Now, I know there are real benefits to breathing deeply so don't get all yoga on me, but to be honest, at the time, it just seemed like a chore and I wished I didn't have the added stress of having to breath deeply iyswim.