How inportant is the specific procedure for hand wrapping with tefillin?

I cant help but notice that a lot of people do it differently, and it seems most pronounced when the wrapping gets to the fingers and hand. Like sometimes i see three wraps around the middle finger, or sometimes three wraps with the middle wrap also going around the ring finger too, and sometimes a shin is made on the hand but not always. Is the actual specific way of wrapping the tefillin at that point not significant? And if it is, why all the difference? Whats right?