Good advice BKR, Judobum, and others!
I am not aware of a general hierarchy of grips, but there a number of players (some well below the competitive ability of Jimmy Pedro) who have a fairly sophisticated gripping strategy that is designed to lead them to a successful tokui waza.
I think of it as a shooter who gets into position, establishes a proper sight picture, then squeezes the trigger. If they hit the bull's eye - Ippon!
I wanted to edit this post, but waited too long.
Originally Posted by BKR
The Pedro DVD has his system, developed by he Dad, Jim Pedro Sr. That has some principles gripping within that system. They can be applied from a basic level to the most advanced level. I think that if anybody wants, they can go to the USJA website and find the simple core of the system in the coaching section (you might have to hunt around a bit).