How to open car when the keys are locked in the car

Straighten out a wire hanger. Then bend one end of the hanger to form either a hook or a triangular handle.
If the car is an older model, pry open a window by slipping a putty knife between the window and the door.
Slip the bent wire hanger through the window opening.
Maneuver the hanger down along the window. Attempt to either pull up the door lock or push the lock button, depending on your car's lock style.

You can also use a blood pressure cuff to form a gap between the door and roof of car. Just pry open enough to stick the cuff in there. Blow up and use the hanger.

Here is an interesting trick using a Tennis Ball. (I have tryed this, and it works well, took me a couple of tries though)

http://www.metacafe.com/watch/410981/blondie_unlocks_car/

I think I will try that. Without locking my keys in the car. Just to see if I can get it to work. lol