I finally learned to grab the door frame before setting foot on the ground, and it never shocked me once I started doing that.

Does that really help ? Mmmm, I must start doing that too then. I get shocked all the time by my car.
I now also get out of my car the way Dignan describes : closing the door by pushing on the glass window.
Of course, this doesn't always solve the problem. It has happened to me a couple of times now that I got out of the car, and closed the cardoor via the glass. No shock, perfect. But then when I inserted my key into the keyhole of the front door of my house (metal on metal), I got one helluva shock.