Gramps is right... usually a spray will work because it will prevent the charge from building up on your body.
Another way is to first open the car door. NEXT hold on to the metal frame of the door (or something else metal on the car that is grounded to the chassis). Then LASTLY as you are holding the metal piece get out.
That way the charge doesn't have a chance to build up on you because it is being constantly dissipated to (chassis) ground.