my experience you have to research into the style the dojo the instructors and every aspect of what you want to learn.all instructors are not good teachers,then again some shodans are exellent teachers.some are in it to make lots of money others just have apassion for the martial arts.Confucius said"when i walk along with two others,they serve as my teachers.I will select their good qualities and follow them,their bad qualties and avoid them"