how does electricity 'decide' on it's pathway?

Instead of thinking your body is empty and that a charged wire has to push electrons one by one through you and into the ground (blood is actually full of charge carriers), a better analogy would be a very long queue of pushy people.
if the entrance to the apple store doesn't open, it doesn't matter how hard the guy at the back pushes--nothing moves. touching your feet to the ground is analagous to opening that front door and allowing the whole queue to move at once, with the pushing (electromotive) force provided by the difference in electric potential between the charged wire and the ground. every electron leaving your foot is pushed and replaced by an electron entering you from the wire.
needless to say if you didnt touch your feet to the ground your entire body assumes the same potential as the wire--you become an extension to that wire, a long queue of impatient charge carriers waiting to burst through any available door. if the wire voltage is high enough you wont need to touch the ground--the high potential will strip electrons from air molecules--corona discharge from your protruding body parts will not be comfortable.
while we're on the subject, dont assume that footwear will always save you. the human body can also function as a capacitor (with your feet and the ground being the coupled conductors and your shoes being the dielectric material). alternating currentscanflow through capacitors.

Thanks and Regards

Apoorva Arora

IIT Roorkee

askIITians Faculty