First step is to ask the top shooters if they know a good instructor. Once you find out about 2-3 of them ask about their expertise, experience and professional RESULTS( his students comments and their scores). I suggest to look for instructors having more than 5 years of experience. Yes, a good shooter can give you some useful tips but a good instructor will teach you methodically based on his experience. Indeed to be a good instructor you have to achieve a certain skill level to teach the fundamentals at least AA or Master class. The 3 days certification process for a level I instructor is not enough to take you where you expect. In conclusion the teaching experience (years of teaching) and the results are the deciding factors of the instructor qualification.